GADD45B (Growth arrest and DNA damage-inducible protein GADD45 beta, also known as MyD118) is a stress-inducible protein that mediates activation of stress-responsive MAPK signaling pathways. The protein binds directly to the N-terminal regulatory domain of MTK1/MEKK4 (MAP3K4), relieving autoinhibition and activating its kinase activity. This leads to downstream activation of both p38 MAPK and JNK cascades in response to environmental stresses including UV irradiation, genotoxic agents (MMS), and gamma irradiation. GADD45B also interacts with MKK7 (MAP2K7), where it blocks kinase activity and suppresses JNK-mediated apoptosis. This dual activity - activating MTK1/MEKK4 while inhibiting MKK7 - positions GADD45B as a key modulator of stress responses and cell fate decisions. The gene is transcriptionally regulated by NF-kB, and its expression is elevated in multiple myeloma where it promotes cancer cell survival by blocking MKK7/JNK-mediated apoptosis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0051726
regulation of cell cycle
|
IBA
GO_REF:0000033 |
KEEP AS NON CORE |
Summary: The GADD45 family is known to regulate cell cycle through interaction with GADD45GIP1/CRIF1 which modulates Cdc2-cyclin B1 and Cdk2-cyclin E activity [PMID:12716909]. IBA evidence from phylogenetic inference is appropriate but this represents a secondary/downstream effect of GADD45B rather than its core molecular function.
Supporting Evidence:
PMID:12716909
Recombinant CRIF1 inhibits the histone H1 kinase activity of immunoprecipitated Cdc2-cyclin B1 and Cdk2-cyclin E, and the inhibitory effects were additive with Gadd45 proteins
|
|
GO:0005634
nucleus
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Nuclear localization is confirmed by direct experimental evidence [PMID:9827804]. IBA provides supporting phylogenetic evidence consistent with experimental data.
Supporting Evidence:
PMID:9827804
Using a yeast two-hybrid method, three related proteins, GADD45alpha (= GADD45), GADD45, (= MyD118), and GADD45gamma, were identified that bound to an N-terminal domain of MTK1
|
|
GO:0005737
cytoplasm
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Cytoplasmic localization is confirmed by direct experimental evidence [PMID:9827804]. IBA provides supporting phylogenetic evidence consistent with experimental data.
Supporting Evidence:
PMID:9827804
These proteins activated MTK1 kinase activity, both in vivo and in vitro
|
|
GO:0005634
nucleus
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: Consistent with IDA-supported annotation from PMID:9827804. InterPro-based inference provides supporting automated evidence for nuclear localization.
|
|
GO:0006915
apoptotic process
|
IEA
GO_REF:0000043 |
MODIFY |
Summary: GADD45B has a complex role in apoptosis. It can promote apoptosis via MTK1/MEKK4 activation leading to p38/JNK stress signaling [PMID:9827804], but also acts as an anti-apoptotic factor by inhibiting MKK7/JNK in cancer contexts [PMID:25314077]. The generic term 'apoptotic process' does not capture this complexity. Should be replaced with the more specific term matching the IDA annotation.
Proposed replacements:
positive regulation of apoptotic process
Supporting Evidence:
PMID:9827804
Expression of the GADD45-like genes induces p38/JNK activation and apoptosis, which can be partially suppressed by coexpression of a dominant inhibitory MTK1 mutant protein
PMID:25314077
GADD45β promotes the survival of MM cells by inhibiting JNK-mediated apoptosis
|
|
GO:0030154
cell differentiation
|
IEA
GO_REF:0000043 |
MARK AS OVER ANNOTATED |
Summary: GADD45B (originally named MyD118 for myeloid differentiation primary response) was identified in myeloid differentiation studies. The keyword-based inference is plausible but lacks direct experimental support for GADD45B specifically being required for differentiation. This may be an over-annotation based on the gene name etymology rather than validated function.
|
|
GO:0046330
positive regulation of JNK cascade
|
IEA
GO_REF:0000117 |
ACCEPT |
Summary: This is well-supported by experimental evidence. GADD45B activates MTK1/MEKK4 which in turn activates both p38 and JNK pathways [PMID:9827804]. However, GADD45B also inhibits JNK via MKK7 binding in certain contexts [PMID:25314077], making this context-dependent. The ARBA prediction is valid for the stress-responsive pathway.
Supporting Evidence:
PMID:9827804
Expression of the GADD45-like genes induces p38/JNK activation and apoptosis
|
|
GO:0051726
regulation of cell cycle
|
IEA
GO_REF:0000002 |
KEEP AS NON CORE |
Summary: Consistent with IBA annotation. InterPro-based inference supports known GADD45 family function in cell cycle regulation via CRIF1 interaction [PMID:12716909].
Supporting Evidence:
PMID:12716909
CRIF1 binds specifically to the Gadd45 family proteins
|
|
GO:1900745
positive regulation of p38MAPK cascade
|
IEA
GO_REF:0000117 |
ACCEPT |
Summary: This is strongly supported by experimental evidence. GADD45B activates MTK1/MEKK4 which activates MKK6, leading to p38 activation [PMID:9827804, PMID:12052864]. ARBA prediction is accurate.
Supporting Evidence:
PMID:12052864
GADD45 proteins bind a site in MTK1 near the inhibitory domain and relieve autoinhibition
|
|
GO:0005515
protein binding
|
IPI
PMID:12052864 Regulation of MTK1/MEKK4 kinase activity by its N-terminal a... |
MODIFY |
Summary: The vague term 'protein binding' should be replaced with a more specific MF term. This paper shows GADD45B binds MTK1/MEKK4 (a MAPKKK) and activates its kinase activity. MTK1/MEKK4 is a MAPKKK (MAP3K4).
Proposed replacements:
mitogen-activated protein kinase kinase kinase binding
Supporting Evidence:
PMID:12052864
By a functional complementation screening with yeast cells, GADD45 proteins (GADD45alpha, beta, and gamma) were identified as MTK1 activators. GADD45 proteins bind a site in MTK1 near the inhibitory domain and relieve autoinhibition
|
|
GO:0005515
protein binding
|
IPI
PMID:16256071 CIN85 regulates the ability of MEKK4 to activate the p38 MAP... |
MODIFY |
Summary: This paper shows CIN85 regulates MEKK4 activation by GADD45 proteins. The protein binding annotation is too vague - this involves the MTK1/MEKK4 activation pathway.
Proposed replacements:
mitogen-activated protein kinase kinase kinase binding
Supporting Evidence:
PMID:16256071
CIN85 was also shown to regulate the activation of MEKK4 by GADD45 proteins and promote multi-ubiquitination of MEKK4
|
|
GO:0005515
protein binding
|
IPI
PMID:25314077 Cancer-selective targeting of the NF-κB survival pathway wit... |
MODIFY |
Summary: This paper shows GADD45B binds directly to MKK7 and blocks its catalytic activity. MKK7 is a MAPKK (MAP2K7). Should be annotated to a more specific term.
Proposed replacements:
mitogen-activated protein kinase kinase binding
Supporting Evidence:
PMID:25314077
GADD45β inhibits apoptosis by suppressing JNK signaling. It mediates this function by binding to the JNK kinase MKK7 and blocking its enzymatic activity by engaging the kinase catalytic pocket
|
|
GO:0005515
protein binding
|
IPI
PMID:32296183 A reference map of the human binary protein interactome. |
REMOVE |
Summary: This is a large-scale binary protein interactome study (HuRI). Generic 'protein binding' from high-throughput studies is not informative without mechanistic context.
Reason: High-throughput interactome study. Specific interactions should be curated from focused literature with mechanistic context rather than generic protein binding.
Supporting Evidence:
PMID:32296183
Here we present a human 'all-by-all' reference interactome map of human binary protein interactions, or 'HuRI'. With approximately 53,000 protein-protein interactions, HuRI has approximately four times as many such interactions as there are high-quality curated interactions from small-scale studies
|
|
GO:0005515
protein binding
|
IPI
PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling... |
REMOVE |
Summary: This is BioPlex 3.0, another large-scale protein interactome study. Same rationale as PMID:32296183 - generic protein binding from HT studies is not informative.
Reason: High-throughput interactome study. Specific interactions should be curated from focused literature with mechanistic context.
Supporting Evidence:
PMID:33961781
Through affinity-purification mass spectrometry, we have created two proteome-scale, cell-line-specific interaction networks. The first, BioPlex 3.0, results from affinity purification of 10,128 human proteins-half the proteome-in 293T cells and includes 118,162 interactions among 14,586 proteins
|
|
GO:0005634
nucleus
|
IDA
PMID:9827804 A family of stress-inducible GADD45-like proteins mediate ac... |
ACCEPT |
Summary: Direct experimental evidence for nuclear localization. This is a core localization for GADD45B's function in stress response signaling.
Supporting Evidence:
PMID:9827804
Using a yeast two-hybrid method, three related proteins, GADD45alpha (= GADD45), GADD45, (= MyD118), and GADD45gamma, were identified that bound to an N-terminal domain of MTK1
|
|
GO:0005737
cytoplasm
|
IDA
PMID:9827804 A family of stress-inducible GADD45-like proteins mediate ac... |
ACCEPT |
Summary: Direct experimental evidence for cytoplasmic localization. GADD45B is found in both nucleus and cytoplasm, consistent with its role in signaling between cellular compartments.
Supporting Evidence:
PMID:9827804
These proteins activated MTK1 kinase activity, both in vivo and in vitro
|
|
GO:0043065
positive regulation of apoptotic process
|
IDA
PMID:9827804 A family of stress-inducible GADD45-like proteins mediate ac... |
ACCEPT |
Summary: Well-supported by experimental evidence showing expression of GADD45-like genes induces p38/JNK activation and apoptosis. This reflects GADD45B's pro-apoptotic activity through MTK1/MEKK4 activation in response to stress.
Supporting Evidence:
PMID:9827804
Expression of the GADD45-like genes induces p38/JNK activation and apoptosis, which can be partially suppressed by coexpression of a dominant inhibitory MTK1 mutant protein
|
|
GO:0046330
positive regulation of JNK cascade
|
IDA
PMID:9827804 A family of stress-inducible GADD45-like proteins mediate ac... |
ACCEPT |
Summary: Well-supported by direct experimental evidence showing GADD45-like proteins mediate activation of the p38/JNK pathway via MTK1/MEKK4. This is a core function.
Supporting Evidence:
PMID:9827804
Expression of the GADD45-like genes induces p38/JNK activation and apoptosis
|
|
GO:1900745
positive regulation of p38MAPK cascade
|
IDA
PMID:9827804 A family of stress-inducible GADD45-like proteins mediate ac... |
ACCEPT |
Summary: Well-supported by direct experimental evidence [PMID:9827804]. Activation of MTK1/MEKK4 by GADD45B leads to p38 MAPK activation. This is a core function.
Supporting Evidence:
PMID:9827804
The stress-responsive p38 and JNK MAPK pathways regulate cell cycle and apoptosis. A human MAPKKK, MTK1 (= MEKK4), mediates activation of both p38 and JNK in response to environmental stresses
|
|
GO:0043066
negative regulation of apoptotic process
|
IDA
PMID:25314077 Cancer-selective targeting of the NF-κB survival pathway wit... |
NEW |
Summary: GADD45B suppresses JNK-mediated apoptosis by directly binding and inhibiting MKK7. This anti-apoptotic function is context-dependent, particularly relevant in NF-kB-driven cancer cells like multiple myeloma.
Supporting Evidence:
PMID:25314077
GADD45β suppresses JNK signaling and apoptosis by blocking MKK7 via direct physical interaction
file:human/GADD45B/GADD45B-deep-research-perplexity.md
GADD45B has also been identified as a promoter of cell survival through inhibition of JNK activation in multiple contexts
|
Q: How is the switch between GADD45B's pro-apoptotic function (MTK1/MEKK4 activation) and anti-apoptotic function (MKK7 inhibition) regulated in different cellular contexts?
Q: What is the structural basis for GADD45B's selective inhibition of MKK7 versus its activation of MTK1/MEKK4?
Experiment: Solve the structure of GADD45B in complex with MTK1 and separately with MKK7 to understand the molecular basis for its opposing effects on these two kinases.
Type: protein structure
Experiment: Determine the relative binding affinities of GADD45B for MTK1 versus MKK7 and how these are modulated by NF-kB pathway activation.
Type: functional assay
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Plan overview
- Verified identity: GADD45B (human; UniProt O75293) encodes growth arrest and DNA damage-inducible protein beta (GADD45β; a.k.a. MyD118), a small, acidic, stress-induced protein of the GADD45 family that acts primarily as a non-enzymatic adaptor in stress and immune signaling. Family-level reviews and recent literature confirm nuclear/cytoplasmic localization, MAPK and NF-κB pathway modulation, and epigenetic roles including active DNA demethylation (Frontiers in Neuroscience, 2024; Frontiers in Immunology, 2025) (huang2024advancesinthe pages 1-2, ma2025growtharrestand pages 1-2).
Comprehensive research report on human GADD45B (GADD45β; UniProt O75293)
1) Key concepts and definitions
- Identity and family: GADD45B is one of three mammalian GADD45 proteins (α/β/γ), small (~18 kDa), highly acidic, evolutionarily conserved stress sensors induced by genotoxic and physiological stress. They lack intrinsic enzymatic activity and function via protein–protein interactions (e.g., with PCNA, CDK1/cyclin B1, p21, and MAPK components), positioning them as adaptor/scaffold proteins in DNA repair, cell-cycle checkpoints, and stress signaling (Frontiers in Immunology, 2025; doi:10.3389/fimmu.2025.1513069, published Feb 2025; URL: https://doi.org/10.3389/fimmu.2025.1513069) (ma2025growtharrestand pages 1-2, ma2025growtharrestand pages 12-13).
- Subcellular localization: GADD45 proteins are predominantly nuclear but can be found in both nucleus and cytoplasm; GADD45β is described as a stress-responsive nuclear protein with reported nuclear/cytoplasmic distribution (Frontiers in Neuroscience, 2024; doi:10.3389/fnins.2024.1349409, published Jan 2024; URL: https://doi.org/10.3389/fnins.2024.1349409) (huang2024advancesinthe pages 1-2, ma2025growtharrestand pages 1-2).
- Pathway roles: The family integrates stress signals into MAPK cascades (JNK and p38) through interactions with upstream MAP3Ks (e.g., MTK1/MEKK4) and modulates NF-κB signaling. GADD45β participates in DNA damage response, checkpoint control (S and G2/M), apoptosis/survival decisions, and immune regulation (Frontiers in Neuroscience, 2024; Frontiers in Immunology, 2025) (huang2024advancesinthe pages 1-2, ma2025growtharrestand pages 12-13, ma2025growtharrestand pages 1-2).
- Epigenetic regulation: GADD45 proteins facilitate active DNA demethylation by interacting with DNA demethylation machinery, thereby regulating gene expression programs; Gadd45b is specifically implicated in activity-dependent demethylation in neurons (Frontiers in Neuroscience, 2024; published Jan 2024) (huang2024advancesinthe pages 1-2, huang2024advancesinthe pages 14-14).
2) Primary molecular functions and mechanisms (current understanding)
- Non-enzymatic adaptor in MAPK signaling: GADD45β modulates MAPK pathways by interacting with upstream MAP3Ks (e.g., MTK1/MEKK4), influencing JNK and p38 activation states, thereby affecting apoptosis, differentiation, and stress responses (Frontiers in Neuroscience, 2024; Frontiers in Immunology, 2025) (huang2024advancesinthe pages 1-2, ma2025growtharrestand pages 12-13).
- NF-κB pathway integration: GADD45β expression is regulated by NF-κB during acute inflammation, and GADD45β can interface with NF-κB signaling networks that determine immune cell phenotypes and survival under inflammatory stress (Frontiers in Immunology, 2025; published Feb 2025) (ma2025growtharrestand pages 13-13).
- DNA repair and checkpoint control: GADD45 proteins interact with PCNA and CDK complexes, supporting roles in nucleotide excision repair and in enforcing S and G2/M checkpoints following DNA damage (Frontiers in Immunology, 2025) (ma2025growtharrestand pages 12-13, ma2025growtharrestand pages 1-2).
- Epigenetic/active DNA demethylation: In neurons, Gadd45b is induced by activity and promotes DNA demethylation at specific promoters (e.g., Bdnf), coupling synaptic activity to transcriptional plasticity and adult neurogenesis (Frontiers in Neuroscience, 2024; published Jan 2024) (huang2024advancesinthe pages 14-14).
3) Biological processes, cellular context, and localization
- Cellular localization and context: Predominantly nuclear with nuclear/cytoplasmic distribution, consistent with roles at DNA replication/repair foci and signaling hubs (Frontiers in Neuroscience, 2024; Frontiers in Immunology, 2025) (huang2024advancesinthe pages 1-2, ma2025growtharrestand pages 1-2).
- Stress response and survival/apoptosis: GADD45β influences cell survival under genotoxic stress by shaping JNK/p38 outputs; family members contribute to checkpoint enforcement and can confer protection from apoptosis in certain contexts (Frontiers in Immunology, 2025) (ma2025growtharrestand pages 12-13, ma2025growtharrestand pages 1-2).
- Immunity/inflammation: GADD45β modulates innate and adaptive immune responses, including cytokine signaling (e.g., IL-18) and NF-κB–dependent programs that regulate inflammatory outcomes and autoimmunity (Frontiers in Immunology, 2025) (ma2025growtharrestand pages 13-13, ma2025growtharrestand pages 12-13).
- Neurobiology and plasticity: Gadd45b is linked to activity-dependent epigenetic remodeling, adult neurogenesis, and behavioral plasticity; dysregulation of GADD45β expression is reported across neuropsychiatric and neurodegenerative conditions (e.g., MDD, PTSD, BD, Parkinson’s disease), and in addiction-related adaptations (Frontiers in Neuroscience, 2024; published Jan 2024; URL: https://doi.org/10.3389/fnins.2024.1349409) (huang2024advancesinthe pages 10-12, huang2024advancesinthe pages 14-14, huang2024advancesinthe pages 14-15).
4) Recent developments and latest research (emphasis 2023–2024)
- 2024 expert review (CNS focus): A comprehensive review synthesizes GADD45 family roles in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders, detailing GADD45β’s nuclear localization, stress signaling via MAPK and NF-κB, and its function in activity-dependent demethylation and neuroplasticity. It compiles evidence for altered GADD45β expression across CNS disorders and highlights the family as potential therapeutic targets for CNS disease (Frontiers in Neuroscience, Jan 2024; doi:10.3389/fnins.2024.1349409) (huang2024advancesinthe pages 1-2, huang2024advancesinthe pages 10-12, huang2024advancesinthe pages 14-14).
- Immune/inflammation perspective: A 2025 immunology review (capturing 2023–2024 literature) summarizes GADD45B’s adaptor functions at the nexus of MAPK and NF-κB, roles in checkpoint control, and immunomodulatory effects in inflammatory and autoimmune disease models (Frontiers in Immunology, Feb 2025; doi:10.3389/fimmu.2025.1513069) (ma2025growtharrestand pages 12-13, ma2025growtharrestand pages 1-2, ma2025growtharrestand pages 13-13).
5) Current applications and real-world implementations
- Biomarker and disease association: Integrative analyses and reviews implicate GADD45B dysregulation in human disease, including neurological disorders and inflammatory pathologies, supporting exploration of GADD45B as a biomarker candidate in specific contexts (Frontiers in Neuroscience, 2024; Frontiers in Immunology, 2025) (huang2024advancesinthe pages 10-12, ma2025growtharrestand pages 13-13, huang2024advancesinthe pages 1-2).
- Therapeutic targeting concepts: Expert authors emphasize the therapeutic potential of modulating GADD45 family function in CNS diseases and inflammatory conditions; while concrete drug examples targeting GADD45B are not detailed in the cited 2023–2024 sources here, the mechanistic positioning of GADD45B within MAPK and NF-κB networks highlights tractable intervention points (Frontiers in Neuroscience, 2024; Frontiers in Immunology, 2025) (huang2024advancesinthe pages 1-2, ma2025growtharrestand pages 12-13, ma2025growtharrestand pages 13-13).
6) Expert opinions and analysis
- Consensus from recent reviews: GADD45B is viewed as a rapid-response, non-enzymatic adaptor integrating DNA damage and inflammatory/physiological stress into MAPK and NF-κB signaling, linking environmental stimuli to gene expression programs (including active DNA demethylation) and cell-fate control. The breadth of roles across immunity and neurobiology suggests context-dependent pro-survival, pro-apoptotic, or plasticity-promoting functions, reinforcing careful tissue- and stimulus-specific investigation for translational development (Frontiers in Neuroscience, 2024; Frontiers in Immunology, 2025) (huang2024advancesinthe pages 1-2, ma2025growtharrestand pages 12-13, huang2024advancesinthe pages 14-14, ma2025growtharrestand pages 13-13).
7) Relevant statistics and data from recent studies
- Neuropsychiatric and addiction models: The 2024 CNS review summarizes multiple primary studies reporting disorder- and region-specific dysregulation of GADD45β (e.g., decreases in MDD and PTSD prefrontal/limbic regions; increases in addiction-related brain regions after acute cocaine), and functional knockdown experiments that attenuate cocaine-induced behavioral and transcriptional responses (Frontiers in Neuroscience, 2024; Jan 2024) (huang2024advancesinthe pages 10-12).
- Epigenetic plasticity: Foundational experiments summarized in 2024 identify activity-induced Gadd45b as a regulator of promoter demethylation (e.g., Bdnf) and adult neurogenesis, establishing a quantitative mechanistic link between neuronal activity and chromatin remodeling (Frontiers in Neuroscience, 2024; Jan 2024) (huang2024advancesinthe pages 14-14).
8) Notes on domain and structural inferences
- Protein family/domains: While recent reviews emphasize function over structure, GADD45 proteins share a conserved fold associated with nucleic acid- and protein-binding and are annotated with interactions at replication/repair machinery and MAPK pathway components, consistent with the UniProt domain annotations and the family’s adaptor role (Frontiers in Immunology, 2025; Frontiers in Neuroscience, 2024) (ma2025growtharrestand pages 1-2, huang2024advancesinthe pages 1-2).
Limitations and scope
- This synthesis is grounded in recent peer-reviewed reviews from 2024–2025 and focuses on human GADD45B. Certain classic mechanistic specifics such as direct binding interfaces to MKK7 in human cells and specific clinical-stage inhibitors were not detailed in the evidence retrieved here; thus, translational claims are framed at a conceptual level pending direct primary citations (huang2024advancesinthe pages 1-2, ma2025growtharrestand pages 12-13, ma2025growtharrestand pages 1-2, ma2025growtharrestand pages 13-13).
Cited sources with URLs and publication dates
- Huang M, Wang J, Liu W, Zhou H. Advances in the role of the GADD45 family in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. Frontiers in Neuroscience. Jan 2024. URL: https://doi.org/10.3389/fnins.2024.1349409 (huang2024advancesinthe pages 1-2, huang2024advancesinthe pages 14-15, huang2024advancesinthe pages 10-12, huang2024advancesinthe pages 14-14)
- Ma Y, Hossen MM, Huang JJ, et al. Growth arrest and DNA damage-inducible 45: a new player on inflammatory diseases. Frontiers in Immunology. Feb 2025. URL: https://doi.org/10.3389/fimmu.2025.1513069 (ma2025growtharrestand pages 12-13, ma2025growtharrestand pages 1-2, ma2025growtharrestand pages 13-13)
- Additional context from the above reviews integrates earlier primary studies (pre-2023) on activity-dependent demethylation and MAPK/NF-κB mechanisms, summarized within these 2024–2025 articles (huang2024advancesinthe pages 1-2, huang2024advancesinthe pages 14-14, ma2025growtharrestand pages 12-13).
References
(huang2024advancesinthe pages 1-2): Mengbing Huang, Ji Wang, Wei Liu, and Hongyan Zhou. Advances in the role of the gadd45 family in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. Frontiers in Neuroscience, Jan 2024. URL: https://doi.org/10.3389/fnins.2024.1349409, doi:10.3389/fnins.2024.1349409. This article has 12 citations and is from a peer-reviewed journal.
(ma2025growtharrestand pages 1-2): Yanmei Ma, Md Munnaf Hossen, Jennifer Jin Huang, Zhihua Yin, Jing Du, Zhizhong Ye, Miaoyu Zeng, and Zhong Huang. Growth arrest and dna damage-inducible 45: a new player on inflammatory diseases. Frontiers in Immunology, Feb 2025. URL: https://doi.org/10.3389/fimmu.2025.1513069, doi:10.3389/fimmu.2025.1513069. This article has 3 citations and is from a peer-reviewed journal.
(ma2025growtharrestand pages 12-13): Yanmei Ma, Md Munnaf Hossen, Jennifer Jin Huang, Zhihua Yin, Jing Du, Zhizhong Ye, Miaoyu Zeng, and Zhong Huang. Growth arrest and dna damage-inducible 45: a new player on inflammatory diseases. Frontiers in Immunology, Feb 2025. URL: https://doi.org/10.3389/fimmu.2025.1513069, doi:10.3389/fimmu.2025.1513069. This article has 3 citations and is from a peer-reviewed journal.
(huang2024advancesinthe pages 14-14): Mengbing Huang, Ji Wang, Wei Liu, and Hongyan Zhou. Advances in the role of the gadd45 family in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. Frontiers in Neuroscience, Jan 2024. URL: https://doi.org/10.3389/fnins.2024.1349409, doi:10.3389/fnins.2024.1349409. This article has 12 citations and is from a peer-reviewed journal.
(ma2025growtharrestand pages 13-13): Yanmei Ma, Md Munnaf Hossen, Jennifer Jin Huang, Zhihua Yin, Jing Du, Zhizhong Ye, Miaoyu Zeng, and Zhong Huang. Growth arrest and dna damage-inducible 45: a new player on inflammatory diseases. Frontiers in Immunology, Feb 2025. URL: https://doi.org/10.3389/fimmu.2025.1513069, doi:10.3389/fimmu.2025.1513069. This article has 3 citations and is from a peer-reviewed journal.
(huang2024advancesinthe pages 10-12): Mengbing Huang, Ji Wang, Wei Liu, and Hongyan Zhou. Advances in the role of the gadd45 family in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. Frontiers in Neuroscience, Jan 2024. URL: https://doi.org/10.3389/fnins.2024.1349409, doi:10.3389/fnins.2024.1349409. This article has 12 citations and is from a peer-reviewed journal.
(huang2024advancesinthe pages 14-15): Mengbing Huang, Ji Wang, Wei Liu, and Hongyan Zhou. Advances in the role of the gadd45 family in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. Frontiers in Neuroscience, Jan 2024. URL: https://doi.org/10.3389/fnins.2024.1349409, doi:10.3389/fnins.2024.1349409. This article has 12 citations and is from a peer-reviewed journal.
GADD45B (Growth Arrest and DNA Damage-Inducible Protein Beta), also known by its alternative designation MyD118 (Myeloid Differentiation Primary Response Protein 118), is a small, highly conserved nuclear protein that functions as a critical stress sensor and signal transducer in human cells[1][4][18]. This 18-kilodalton acidic protein belongs to the GADD45 family of genes, which comprises three closely related members designated GADD45A, GADD45B, and GADD45G, each with distinct but overlapping functions in cellular stress responses[11][26]. The GADD45B gene is located on human chromosome 19 (specifically 2,476,122-2,478,805 forward strand in the GRCh38 assembly) and contains nine transcript splice variants that expand its functional diversity[6]. GADD45B serves as a molecular hub integrating multiple stress signals and directing cellular responses through activation of the p38/JNK mitogen-activated protein kinase (MAPK) pathway, modulation of cell cycle checkpoints, facilitation of DNA repair mechanisms, and regulation of epigenetic modifications through DNA demethylation. The protein's involvement extends across diverse biological processes including apoptosis, cell survival, neurogenesis, immune regulation, and wound healing, with dysregulation implicated in various disease states including cancer, neuropsychiatric disorders, and metabolic dysfunction.
The structural organization of GADD45B provides critical insights into its biochemical functions and interactions with binding partners. The protein comprises a compact α/β sandwich structure featuring a central five-stranded mixed β-sheet flanked by α-helices on either side[39][42]. The crystal structure of GADD45 proteins reveals a unique dimerization interface involving helices α2 and α3, which form a four-helix bundle with predominantly hydrophobic interactions[42]. Specifically, residues Ile-76 through Leu-80 of helix α3 participate in the dimerization interface, and mutational analysis demonstrates that an L80E point mutation is sufficient to block dimerization while preserving the monomer's three-dimensional fold[42]. The dimerization interface involves the most highly conserved regions among all GADD45 family isoforms, which is consistent with the critical importance of this structural feature for biological function[39]. A conserved and highly acidic patch is present in the central region of the dimer, encompassing critical residues such as Glu87 and Asp89, which form a putative binding interface for interaction with cell-cycle-regulatory proteins, DNA repair machinery components, and apoptotic mediators[42][59]. This acidic patch serves as a key functional domain for interactions with proliferating cell nuclear antigen (PCNA), the CDK inhibitor p21, and the cell cycle kinase cdc2[39][42]. The protein structure incorporates ribosomal protein-associated domains (ribosomal_L7Ae, Ribosomal_eL30-like superfamily, and Ribosomal_eL8/eL30/eS12/Gad45 domains), suggesting evolutionary relationships with ribosomal proteins and implying potential roles in translation regulation or ribosomal function[2]. The dimerization of GADD45 proteins is essential for their biological functions, as cellular assays demonstrate that dimerization is necessary for both apoptosis promotion and growth inhibition in hepatoma cells, indicating that the parallel dimer represents the active functional form[42][59].
GADD45B functions as a stress-responsive signal transducer that initiates cellular protective or death responses through activation of critical MAPK signaling cascades. The canonical function of GADD45B involves direct binding to and activation of MTK1 (also designated MEKK4), a mitogen-activated protein kinase kinase kinase that serves as an upstream activator of both p38 and JNK MAPK pathways[7][11][18]. Upon stress stimulation, GADD45B binds to MTK1/MEKK4, enhancing the autophosphorylation and kinase activity of this upstream regulator, which subsequently leads to phosphorylation and activation of downstream p38 and JNK kinases[7][20]. The activation of p38/JNK pathways by GADD45B coordinates complex cellular responses including growth suppression, differentiation, cell cycle arrest, apoptosis, and innate immune activation[11][26]. Beyond its role in p38/JNK activation, GADD45B participates in regulating extracellular signal-regulated kinase (ERK) pathways, though in specific contexts it can either activate or inhibit JNK signaling depending on cell type and stimulus[20][21]. GADD45B has also been identified as a positive regulator of interferon signaling through facilitation of stress granule formation via interaction with the RNA-binding protein G3BP (Ras-GTPase-activating protein-binding protein)[25][28]. Additionally, GADD45B acts as a downstream target of the transcription factor NF-κB, and the GADD45B gene contains three κB sites within its promoter region, distinguishing it from GADD45A and GADD45G whose promoters lack such sites[20][37]. This NF-κB-GADD45B-MAPK regulatory axis represents a critical node in the integration of inflammatory signals with stress responses[20][37]. The protein also modulates the transforming growth factor-β (TGF-β) signaling pathway through competitive interaction with Smad7, thereby preventing the proteasomal degradation of the TGF-β receptor type 1 and promoting epithelial restitution and wound healing processes[35].
GADD45B plays a significant role in cell cycle regulation, particularly in the establishment and maintenance of G2/M checkpoints in response to genotoxic stress. The protein interacts physically with the cdc2/cyclin B1 complex (also known as CDK1/cyclin B1), a key regulator of the G2 to M phase transition[43][46]. GADD45B, along with GADD45A and GADD45G, inhibits the kinase activity of the cdc2/cyclin B1 complex, though the magnitude of inhibition varies among family members, with GADD45B showing approximately 30% inhibition compared to GADD45A which demonstrates up to 80% inhibition[20]. The interaction between GADD45B and cdc2 results in disruption of the complex in some cellular contexts, thereby blocking progression through the G2/M checkpoint[43]. Evidence from studies utilizing knockout mice and dominant-negative approaches reveals that GADD45 proteins, including GADD45B, are essential for G2/M checkpoint activation in response to specific types of genotoxic stress, including methyl methane sulfonate (MMS) and ultraviolet (UV) radiation, though cells deficient in GADD45 proteins retain some G2/M checkpoint function following ionizing radiation[8][21]. GADD45B also engages in interactions with p21/WAF1/CIP1, a CDK inhibitor that functions downstream of p53, with the central region of GADD45B mediating this critical interaction[20][37]. Furthermore, GADD45B binds to PCNA, the sliding clamp protein essential for DNA replication and repair, and this interaction modulates PCNA's function from a simple processivity factor to a regulator of cellular division[13][20]. The interaction between GADD45B and PCNA appears to compete with p21 binding to PCNA, suggesting a complex regulatory relationship among these proteins in controlling DNA replication and cell cycle progression[13].
A particularly significant and well-characterized function of GADD45B involves its direct participation in active DNA demethylation processes, particularly in the context of neuronal activity-dependent gene expression in the adult brain. GADD45B is required for activity-induced demethylation of specific gene promoters, including the regulatory regions of brain-derived neurotrophic factor (BDNF) and fibroblast growth factor-1 (FGF-1), which are critical for adult neurogenesis[18][19]. Following neuronal stimulation or electroconvulsive therapy in mouse models, GADD45B expression is rapidly induced, and the protein becomes associated with chromatin regions containing these target genes[19]. The demethylation activity of GADD45B appears to involve interaction with DNA methyltransferase-1 (DNMT1) and potentially with ten-eleven translocation (TET) enzymes, though the precise molecular mechanisms remain incompletely characterized[36]. Single-cell transcriptomic studies reveal that GADD45B subcellular localization correlates with specific viral gene expression programs in herpes simplex virus-1 (HSV-1) infected neurons, with cytoplasmic localization of GADD45B mRNA associating with viral DNA synthesis and successful viral reactivation[9]. In the context of herpes virus infection, distinct GADD45B subcellular localization patterns serve as biomarkers for successful versus aborted viral reactivation states, with nuclear punctate GADD45B staining correlating with latent or abortively reactivating neurons[9]. The activity-induced demethylation function of GADD45B represents a key mechanism through which transient neuronal activation achieves long-lasting effects on neural plasticity and memory formation, providing a bridge between immediate-early gene induction and sustained epigenetic reprogramming[19]. In the context of chronic social defeat stress (CSDS), GADD45B mediates depressive-like behaviors through DNA demethylation of specific gene loci in the nucleus accumbens, including the GABAergic gene GAD1, the BDNF receptor NTRK2, and developmental genes such as DLX5[22].
GADD45B functions primarily as a nuclear protein, with its localization predominantly within the nucleoplasm under basal conditions[12][48]. However, stress stimulation induces dynamic redistribution of GADD45B between nuclear and cytoplasmic compartments, with specific subcellular localization patterns reflecting the type of stress and cellular response pathway activated[9][12]. In latently HSV-1 infected neurons, GADD45B localizes to both nuclear and cytoplasmic compartments, with distinct localization changes following viral reactivation stimulation—neurons undergoing active viral DNA synthesis display predominantly cytoplasmic GADD45B localization, while neurons that fail to reactivate exhibit nuclear punctate or pan-nuclear staining patterns[9]. This dynamic localization represents approximately 40% reactivation efficiency when GADD45B cytoplasmic localization is used as a biomarker[9]. At the tissue level, GADD45B expression is broadly distributed across human tissues but shows preferential expression in specific tissues relevant to its various biological functions. The protein atlas indicates high expression in the brain (particularly hippocampal formation, amygdala, cerebral cortex, and other regions), various endocrine tissues (thyroid, adrenal, pituitary glands), and lymphoid tissues (thymus, spleen, lymph nodes)[5][12][45][48]. Gastrointestinal tissues including the esophagus, stomach, colon, and small intestine express GADD45B at detectable levels, consistent with its identified roles in wound healing and epithelial restitution[35][48]. The nucleoplasmic localization is particularly pronounced, with no significant evidence for nucleolar or cytoplasmic sequestration under basal conditions, though the protein possesses intrinsic capacity for dynamic translocation in response to cellular stress[12][48].
GADD45B expression is rapidly and dramatically induced in response to diverse environmental and physiological stressors, positioning it as a critical stress sensor in mammalian cells. The gene responds to multiple categories of stress signals including DNA-damaging agents (ionizing radiation, UV radiation, chemical mutagens such as methyl methane sulfonate), oxidative stressors (hydrogen peroxide, arsenite, heavy metals), inflammatory cytokines (IL-6, TNF-α, LPS), immunosuppressive signals (TGF-β), growth factor withdrawal, hypoxia, and metabolic stress[11][26][27]. Each member of the GADD45 family displays a unique temporal and intensity pattern of induction in response to specific stressors, indicating differential regulation by distinct transcription factors and signaling pathways[11][24][26]. GADD45B is notably induced by TGF-β in multiple cell types, a property shared with GADD45G but not with GADD45A, suggesting unique regulatory mechanisms for GADD45B in immune and developmental contexts[24][26]. In myeloid cells, GADD45B functions as a differentiation primary response gene that is induced immediately upon hematopoietic cytokine exposure and subsequently down-regulated[24][32]. The regulation of GADD45B expression involves multiple transcriptional regulators including NF-κB, Egr-1, p53 (though GADD45B can be induced in a p53-independent manner), and other stress-responsive transcription factors[26][37][41][50]. At the posttranscriptional level, GADD45B mRNA stability is regulated by RNA-stabilizing proteins and microRNAs, with ROS-dependent mechanisms modulating mRNA half-life in specific signaling contexts[20]. In hepatic tissue, PPARα activation promotes GADD45B induction through an unusual mechanism involving PPARα-mediated ubiquitination and degradation of STAT3, which otherwise serves as a transcriptional repressor of the GADD45B gene[41][58]. The responsiveness of GADD45B to such diverse stimuli reflects its central role as a stress-responsive hub protein that translates various danger signals into coordinated cellular responses.
GADD45B exhibits complex, context-dependent roles in regulating apoptosis and cell survival, with the outcome of apoptosis versus survival determination depending on cell type, the nature of stress stimulus, and the particular GADD45B-binding partners engaged. In multiple studies, GADD45B promotes apoptosis through p38/JNK MAPK pathway activation in response to genotoxic stress, TNF-α, Fas ligation, and other pro-death stimuli[11][27][51]. In hepatocyte AML12 cells stimulated with Fas antibody, GADD45B mediates apoptosis through a mechanism involving p38-mediated retinoblastoma (Rb) protein hyperphosphorylation, with GADD45B functioning as an adaptor protein that enhances the interaction between p38 kinase and the Rb protein substrate[51]. Notably, in these cells, GADD45B depletion suppresses p38-mediated Rb phosphorylation without inhibiting p38 phosphorylation itself, indicating that GADD45B acts downstream of p38 activation to facilitate productive kinase-substrate interactions[51]. In chemotherapy-resistant prostate cancer cells, GADD45B expression is decreased in metastatic tumors compared to localized tumors, and high GADD45B expression increases significantly under environmental stress (hypoxia, low serum, docetaxel exposure) and enhances chemosensitivity by promoting apoptosis through p38/MAPK pathway activation[27]. In contrast, GADD45B has also been identified as a promoter of cell survival through inhibition of JNK activation in multiple contexts. In UV-irradiated hematopoietic cells, GADD45B cooperates with GADD45A to promote cell survival through two distinct mechanisms: GADD45A activates a p38-NF-κB-mediated survival pathway while GADD45B simultaneously inhibits the stress-response MKK4-JNK pathway[21][29]. GADD45B directly binds to MKK7, an upstream activator of JNK, and inhibits its enzymatic activity through interactions with critical residues in the MKK7 catalytic domain[20][35][51]. Furthermore, in murine hepatocyte cells, GADD45B mediates protection against TNF-α-induced apoptosis through this JNK-inhibitory mechanism[35]. Additionally, GADD45B mediates oxidative stress resistance through promoting p53 protein degradation via a Src/PP2A/MDM2-dependent pathway following arsenite exposure, thereby attenuating the proapoptotic function of p53[50][55]. This anti-apoptotic mechanism appears unique to GADD45B, as it differs fundamentally from GADD45A, which promotes apoptosis through p53 stabilization[50][55]. The balance between these pro-apoptotic and anti-apoptotic functions appears to be determined by the specific interaction partners engaged, the particular MAPK pathway branch activated, and the cellular context.
GADD45B plays critical roles in hippocampus-dependent memory formation and adult neurogenesis through its capacity to facilitate DNA demethylation and modify chromatin accessibility. Knockout studies demonstrate that GADD45B-deficient mice exhibit significant deficits in long-term contextual fear conditioning and spatial memory, despite displaying normal short-term contextual memory[57]. Following contextual fear conditioning or environmental context exposure, GADD45B mRNA and protein expression increase markedly in the hippocampus, particularly in the dentate gyrus region[19][57]. The mechanistic basis for GADD45B's role in memory formation involves activity-induced demethylation of specific BDNF promoter regions (particularly regulatory region IX) and FGF-1 promoter sites (specifically brain-specific promoter B), resulting in increased gene expression of these critical neurotropic factors[19]. BDNF is extensively documented to promote dendritic growth and synaptic plasticity in hippocampal neurons, while FGF-1 exhibits robust mitogenic activity on neural progenitor cells, collectively supporting adult neurogenesis and hippocampal-dependent learning[19]. In wild-type mice, electroconvulsive therapy (ECT) markedly increases dendritic length and complexity of newborn neurons in the hippocampus, an effect that is significantly attenuated in GADD45B knockout mice while basal dendritic growth remains unaffected[19]. The demethylation activity of GADD45B appears to represent an active, demethylase-dependent process rather than passive dilution of methylation marks during cell division, as GADD45B operates in differentiated, postmitotic neurons where cell division does not occur[19]. Beyond memory formation, alterations in GADD45B expression have been identified in various neurodevelopmental and neuropsychiatric disorders, including autism spectrum disorder (ASD), schizophrenia (SCZ), bipolar disorder (BD), and attention-deficit/hyperactivity disorder (ADHD)[33][60]. In ASD patients, global GADD45B expression levels are reduced, with particular deficiencies in lymphocyte DNA methylation patterns and frontal cortex neuron histone methylation[33][57][60]. In schizophrenia and bipolar disorder patients, frontal cortex neurons paradoxically display increased GADD45β-positive cells accompanied by reduced BDNF promoter binding and increased 5-methylcytosine at the BDNF promoter, resulting in decreased BDNF expression[33][60]. This apparent contradiction suggests that increased GADD45β presence in psychiatric patients may reflect a compensatory response to a highly methylated cellular environment in which GADD45β expression is upregulated but its demethylating activity is insufficient to overcome excessive methylation[33][60]. In the substantia nigra of Parkinson's disease patients, GADD45β expression is abnormally heightened, implicating it in pathological stress responses associated with neurodegeneration[33][60]. The critical role of GADD45β in hippocampal-dependent cognition also extends to social behavior, as knockout of GADD45B alters social behavior of neonatal rats and reduces expression of psychiatric disorder-associated genes including methyl-CpG-binding protein 2 (MeCP2), Reelin, and BDNF[33][60].
GADD45B functions as a critical regulator of both innate and adaptive immune responses, particularly through its capacity to modulate MAPK signaling pathways in immune cells. In effector T cells, GADD45B and GADD45G activate p38/JNK signaling and promote IFN-γ production, critical for Th1 differentiation and cell-mediated immunity[20][26]. GADD45B has been identified as essential for regulation of type I interferon signaling through a mechanism involving facilitation of stress granule formation via interaction with the RNA-binding protein G3BP[25][28]. During viral or microbial infections, GADD45B-mediated stress granule formation provides a crucial cellular defense mechanism through sequestration of viral mRNAs and translation suppression of viral proteins[25]. In experimental sepsis models, GADD45β-knockout mice exhibit significantly reduced myeloid cell recruitment to the peritoneal cavity following lipopolysaccharide (LPS) stimulation, demonstrating the importance of GADD45B in acute inflammatory responses[35]. Moreover, macrophages and granulocytes from GADD45α/β double-knockout mice display reduced migratory efficiency in chemotactic assays, indicating impaired chemotaxis in response to inflammatory stimuli[35]. In response to acute inflammatory stress and hematopoietic cytokine stimulation, both GADD45a-deficient and GADD45b-deficient mice show significantly reduced percentages of mature macrophages and granulocytes in bone marrow cell populations compared to wild-type controls, implicating GADD45B in myeloid differentiation and acute phase responses[24][32]. The reduced myeloid recovery following myelo-ablation (achieved through 5-fluorouracil treatment) in GADD45B-deficient mice suggests that GADD45B plays a role in maintaining the quiescent stem cell pool and promoting recovery through enhanced progenitor cell survival during stress hematopoiesis[24][32]. At the dendritic cell level, GADD45B regulates dendritic cell cytokine production through MAPK pathway modulation[32].
GADD45B promotes tissue repair and wound healing through its capacity to regulate the TGF-β signaling pathway in epithelial cells. In an experimental colitis model, GADD45β-knockout mice demonstrate hypersusceptibility to disease induction and display accelerated colitis progression with more severe histological scores and greater loss of goblet cells in the colon compared to wild-type controls[35]. The mechanism underlying GADD45β's protective role in colitis involves regulation of TGF-β signaling in colonocytes, where GADD45β competitively binds to the inhibitory Smad7 protein, preventing Smurf-mediated ubiquitination and proteasomal degradation of TGF-β receptor type 1[35]. By stabilizing the TGF-β receptor, GADD45β enhances TGF-β-dependent signaling, leading to increased phosphorylation of Smad2 and Smad3 transcription factors[35]. In cultured intestinal epithelial cells (Caco-2), overexpression of GADD45β enhances the wound closure response to TGF-β stimulation through a mechanism involving enhanced cell migration rather than increased proliferation[35]. This restitution function is particularly evident when proliferation is inhibited by hydroxyurea, demonstrating that GADD45β-induced TGF-β signaling promotes epithelial cell migration to close wounds rather than relying on proliferative expansion[35]. These findings expand the functional repertoire of GADD45β to encompass regenerative medicine and ulcerative colitis pathophysiology, establishing the protein as a potential therapeutic target for inflammatory bowel disease.
GADD45B participates in various metabolic and oxidative stress responses, suggesting roles extending beyond its classical DNA damage response functions. In diabetic kidney disease, GADD45B is significantly upregulated in diabetic kidney tissue, correlating with renal tubular epithelial-mesenchymal transition (EMT) and apoptosis[44]. In cultured kidney proximal tubular epithelial cells (HK-2) exposed to high glucose, GADD45B expression increases substantially, and its overexpression exacerbates glucose-induced EMT and apoptosis through p38 MAPK and JNK pathway activation[44]. Notably, inhibition of p38 MAPK or JNK with specific pharmacological inhibitors alleviates both glucose-induced and GADD45B overexpression-induced renal tubular injury, confirming the critical role of these MAPK pathways in GADD45B-mediated glucose toxicity[44]. This identifies GADD45B as a potential contributor to diabetic kidney injury and a potential therapeutic target in diabetes-associated renal complications. In oxidative stress responses induced by heavy metals such as antimony, the Nrf2-GADD45B signaling axis provides cellular protection through upregulation of antioxidant pathways[31]. In hepatic tissue, oxidative stress activates the GADD45B gene through PPARα-mediated degradation of STAT3, a constitutive repressor of GADD45B, demonstrating that hepatic oxidative stress-induced GADD45B expression links peroxisome proliferator-activated receptor signaling to cell cycle arrest and stress adaptation[41][58]. These diverse metabolic functions suggest that GADD45B functions as a general integrator of various cellular stress signals, coordinating responses to oxidative, metabolic, and genotoxic insults.
GADD45B functions through a complex network of protein-protein interactions that direct its various cellular roles and determine the cellular outcome of GADD45B activation. The protein interacts with multiple binding partners including PCNA, p21/WAF1/CIP1, cdc2/cyclin B1, MTK1/MEKK4, MKK7, ASK1 (apoptosis signal-regulating kinase 1), MAP2K7 (another designation for MKK7), and numerous other signaling proteins[18][49]. The interaction of GADD45B with PCNA occurs through the highly acidic C-terminal region of the protein and results in competition with p21 for PCNA binding[13][20]. In biochemical assays using purified recombinant proteins, GADD45B can be shown to directly bind PCNA through Far-western blotting, and this interaction can be competed away by p21 protein[13]. The PCNA interaction appears important for modulating DNA replication and repair processes in response to cellular stress. The interaction between GADD45B and the central region of p21 represents another critical protein-protein interface, as p21 serves as a universal CDK inhibitor involved in both G1/S and G2/M cell cycle arrest[20][37]. The interaction of GADD45B with the cdc2/cyclin B1 kinase complex (CDK1/cyclin B1) involves direct contact with both the catalytic kinase subunit and the regulatory cyclin B1 component, resulting in inhibition of kinase activity[43][46]. In contrast to its inhibitory effect on cdc2/cyclin B1, GADD45B directly activates the upstream kinase MTK1/MEKK4 through binding and enhancement of autophosphorylation, leading to downstream p38 and JNK activation[7][20]. The interaction between GADD45B and MKK7 represents a potential point of negative regulation, as GADD45B directly binds to MKK7 and inhibits its catalytic activity toward JNK substrates, providing a mechanism through which GADD45B can attenuate JNK signaling in specific cellular contexts[20][35][51]. In Fas-induced apoptosis studies, GADD45B has been shown to interact directly with both p38 kinase and retinoblastoma (Rb) protein, functioning as a molecular adaptor that facilitates p38-mediated Rb phosphorylation[51]. More recently, GADD45B has been identified as an interacting partner of G3BP (Ras-GTPase-associated binding protein), with this interaction promoting stress granule formation and facilitating interferon regulatory factor 3 (IRF3) activation during viral infection[25][28]. Additionally, GADD45β can bind to the NF-κB subunit p65 and facilitate its nuclear localization and transcriptional activity in specific contexts[33]. These diverse protein interactions indicate that GADD45B functions as a hub protein capable of coordinating responses across multiple signaling pathways and cellular processes.
Dysregulation of GADD45B expression has been identified in various human malignancies and disease states, with both loss-of-function and gain-of-function scenarios contributing to pathogenesis. In prostate cancer, GADD45B expression is significantly reduced in metastatic tumors compared to localized tumors, and restoration of GADD45B expression enhances chemosensitivity through promotion of apoptosis[27]. Low GADD45B expression in metastatic prostate cancer correlates with poor prognosis and resistance to environmental stresses and chemotherapy, identifying GADD45B as a potential biomarker for metastatic disease progression[27]. In gastric cancer, GADD45B has been identified as a key gene participating in the carcinogenesis process of chronic atrophic gastritis through p53 signaling pathway alterations[30][52]. In hematologic malignancies, particularly multiple myeloma and activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL), oncogenic NF-κB signaling mediates cancer cell survival through upregulation of GADD45B, which then suppresses apoptosis ensuing from JNK/MAPK pathway activation by inhibiting MKK7[54]. This context represents a tumor-promoting function of GADD45B where NF-κB constitutively activates GADD45B to confer survival advantage to malignant B cells. In neuroblastoma and glioma cells, altered GADD45A expression (a related family member) has been implicated in tumorigenesis, though GADD45B-specific alterations in glioma have not been extensively characterized. In type I interferon signaling, GADD45B plays a crucial regulatory role through facilitation of stress granule formation and IRF3 activation, but aberrant regulation of this pathway in virus-infected or transformed cells could contribute to immune evasion by pathogens or cancers. The role of GADD45B as both a potential tumor suppressor (through enhanced apoptosis in metastatic prostate cancer) and a tumor promoter (through NF-κB-driven survival in hematologic malignancies) demonstrates the context-dependent nature of GADD45B function in cancer biology.
GADD45B belongs to an evolutionarily conserved protein family with representatives identified in diverse species ranging from invertebrates to mammals, suggesting fundamental importance in stress response mechanisms. The GADD45 family demonstrates 55%-57% overall amino acid identity among human family members (GADD45A, GADD45B, and GADD45G), with the highest conservation observed in the helical regions that form the dimerization interface[2][21][24]. The Drosophila melanogaster homolog (D-GADD45, encoded by CG11086) shows strongest amino acid sequence identity with human GADD45γ (31% identity) and contains the characteristic ribosomal protein domain spanning residues 33 through 134[15]. Studies in Drosophila demonstrate that D-GADD45 overexpression in somatic follicle cells triggers apoptosis, while overexpression in germline tissues affects dorsal-ventral polarity of the oocyte through effects on grk RNA localization and anterior-posterior polarity determinants[15]. The JNK pathway genetic interactions are conserved between Drosophila and mammals, as eggshell polarity defects caused by D-GADD45 overexpression are dominantly suppressed by mutations in the JNK pathway, consistent with the mammalian GADD45-MAPK connection[15]. This evolutionary conservation across hundreds of millions of years indicates that the core stress-sensing and MAPK-activating functions of GADD45 proteins represent a fundamental regulatory mechanism that has been maintained through diverse organismal lineages. The presence of conserved ribosomal protein-like domains in GADD45 proteins suggests that this protein family may have evolutionary origins in ribosomal function, with later specialization toward stress signaling roles[2][15].
The multifaceted roles of GADD45B in stress response, immune regulation, and disease pathogenesis position it as a potential therapeutic target for multiple disease contexts. In prostate cancer, particularly metastatic disease and chemotherapy-resistant tumors, therapeutic strategies aimed at increasing GADD45B expression or enhancing its pro-apoptotic signaling could sensitize cancer cells to therapy[27]. In hematologic malignancies where NF-κB-driven GADD45B expression promotes survival, therapeutic inhibition of GADD45B or blockade of its anti-apoptotic interactions with MKK7 or p53-degradation pathways could potentially overcome NF-κB-mediated survival signals[54]. In inflammatory bowel disease, particularly ulcerative colitis, strategies to enhance GADD45B expression or augment its TGF-β signaling functions could promote epithelial restitution and reduce disease severity[35]. In neuropsychiatric disorders characterized by aberrant GADD45B expression and DNA methylation abnormalities, modulation of GADD45B expression or its demethylating activity could potentially correct epigenetic abnormalities and restore normal BDNF signaling[57][60]. In diabetic kidney disease and other metabolic complications of diabetes, inhibition of GADD45B-dependent p38/JNK signaling could reduce glucose-induced EMT and apoptosis of renal tubular epithelial cells[44]. Development of small-molecule inhibitors targeting the dimerization interface of GADD45B or its key protein-protein interaction interfaces (such as the PCNA-binding or MKK7-binding surfaces) could provide therapeutic tools for conditions where GADD45B functions need to be suppressed. Conversely, agents that enhance GADD45B expression, stability, or interactions with pro-apoptotic partners could be beneficial in cancer contexts where GADD45B functions as a tumor suppressor. Given the recent identification of stress granule formation as an important GADD45B function in interferon signaling, pharmacological enhancement of GADD45B-G3BP interactions could potentially enhance antiviral responses during infectious disease[25][28]. Future research should focus on clarifying the structural basis of GADD45B's diverse protein interactions, defining how distinct cellular contexts determine whether GADD45B mediates apoptosis or survival, and developing cell-type-specific and stimulus-specific therapeutic approaches that exploit these contextual distinctions.
GADD45B represents a critical stress-responsive hub protein that integrates multiple danger signals and coordinates complex cellular responses through activation of MAPK signaling pathways, modulation of cell cycle checkpoints, facilitation of DNA repair and epigenetic remodeling, and regulation of apoptotic and survival pathways. The protein's 18-kilodalton structure comprises a conserved α/β sandwich architecture with a critical dimerization interface involving helices α2 and α3, creating an active parallel dimer that displays a highly acidic surface patch essential for binding cell-cycle regulators, DNA repair machinery components, and apoptotic mediators. Primary molecular functions center on direct activation of the MTK1/MEKK4 kinase, which initiates p38 and JNK MAPK signaling cascades that coordinate growth arrest, differentiation, apoptosis, and immune activation. Beyond classical DNA damage responses, GADD45B participates in activity-induced DNA demethylation of specific gene promoters including BDNF and FGF-1, establishing its importance in adult neurogenesis, hippocampus-dependent memory formation, and epigenetic regulation of neuronal plasticity. The protein functions as a stress-responsive regulator of TGF-β signaling through competitive binding to Smad7, thereby promoting epithelial restitution and wound healing processes. GADD45B exhibits context-dependent functions in determining cell fate outcomes, promoting apoptosis through p38-mediated Rb hyperphosphorylation in hepatocytes and docetaxel-treated cancer cells while simultaneously promoting survival through JNK inhibition in hematopoietic cells and TNF-α-exposed fibroblasts. Dysregulation of GADD45B has been implicated in multiple disease states including prostate cancer, hematologic malignancies, inflammatory bowel disease, neurodevelopmental disorders, neuropsychiatric conditions, and metabolic complications of diabetes. The evolutionary conservation of GADD45B across diverse species, combined with its broad tissue distribution and responsiveness to multiple classes of stressors, underscore its fundamental importance in cellular homeostasis and adaptive responses to environmental perturbation. Future therapeutic applications may involve either enhancement of GADD45B pro-apoptotic functions in chemotherapy-resistant cancers or modulation of its demethylating activities in neurodevelopmental and psychiatric disorders, with success requiring careful consideration of cellular context, tissue type specificity, and stimulus-dependent pathway selection.
id: O75293
gene_symbol: GADD45B
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:9606
label: Homo sapiens
description: >-
GADD45B (Growth arrest and DNA damage-inducible protein GADD45 beta, also known
as MyD118)
is a stress-inducible protein that mediates activation of stress-responsive MAPK
signaling
pathways. The protein binds directly to the N-terminal regulatory domain of MTK1/MEKK4
(MAP3K4), relieving autoinhibition and activating its kinase activity. This leads
to
downstream activation of both p38 MAPK and JNK cascades in response to environmental
stresses including UV irradiation, genotoxic agents (MMS), and gamma irradiation.
GADD45B also interacts with MKK7 (MAP2K7), where it blocks kinase activity and suppresses
JNK-mediated apoptosis. This dual activity - activating MTK1/MEKK4 while inhibiting
MKK7 -
positions GADD45B as a key modulator of stress responses and cell fate decisions.
The gene
is transcriptionally regulated by NF-kB, and its expression is elevated in multiple
myeloma
where it promotes cancer cell survival by blocking MKK7/JNK-mediated apoptosis.
existing_annotations:
- term:
id: GO:0051726
label: regulation of cell cycle
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: >-
The GADD45 family is known to regulate cell cycle through interaction with GADD45GIP1/CRIF1
which modulates Cdc2-cyclin B1 and Cdk2-cyclin E activity [PMID:12716909]. IBA
evidence from
phylogenetic inference is appropriate but this represents a secondary/downstream
effect of
GADD45B rather than its core molecular function.
action: KEEP_AS_NON_CORE
supported_by:
- reference_id: PMID:12716909
supporting_text: "Recombinant CRIF1 inhibits the histone H1 kinase activity\
\ of immunoprecipitated Cdc2-cyclin B1 and Cdk2-cyclin E, and the inhibitory\
\ effects were additive with Gadd45 proteins"
- term:
id: GO:0005634
label: nucleus
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: >-
Nuclear localization is confirmed by direct experimental evidence [PMID:9827804].
IBA provides supporting phylogenetic evidence consistent with experimental data.
action: ACCEPT
supported_by:
- reference_id: PMID:9827804
supporting_text: "Using a yeast two-hybrid method, three related proteins, GADD45alpha\
\ (= GADD45), GADD45, (= MyD118), and GADD45gamma, were identified that bound\
\ to an N-terminal domain of MTK1"
- term:
id: GO:0005737
label: cytoplasm
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: >-
Cytoplasmic localization is confirmed by direct experimental evidence [PMID:9827804].
IBA provides supporting phylogenetic evidence consistent with experimental data.
action: ACCEPT
supported_by:
- reference_id: PMID:9827804
supporting_text: "These proteins activated MTK1 kinase activity, both in vivo\
\ and in vitro"
- term:
id: GO:0005634
label: nucleus
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: >-
Consistent with IDA-supported annotation from PMID:9827804. InterPro-based inference
provides supporting automated evidence for nuclear localization.
action: ACCEPT
- term:
id: GO:0006915
label: apoptotic process
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: >-
GADD45B has a complex role in apoptosis. It can promote apoptosis via MTK1/MEKK4
activation leading to p38/JNK stress signaling [PMID:9827804], but also acts
as
an anti-apoptotic factor by inhibiting MKK7/JNK in cancer contexts [PMID:25314077].
The generic term 'apoptotic process' does not capture this complexity. Should
be
replaced with the more specific term matching the IDA annotation.
action: MODIFY
proposed_replacement_terms:
- id: GO:0043065
label: positive regulation of apoptotic process
supported_by:
- reference_id: PMID:9827804
supporting_text: "Expression of the GADD45-like genes induces p38/JNK activation\
\ and apoptosis, which can be partially suppressed by coexpression of a dominant\
\ inhibitory MTK1 mutant protein"
- reference_id: PMID:25314077
supporting_text: "GADD45β promotes the survival of MM cells by inhibiting JNK-mediated\
\ apoptosis"
- term:
id: GO:0030154
label: cell differentiation
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: >-
GADD45B (originally named MyD118 for myeloid differentiation primary response)
was identified in myeloid differentiation studies. The keyword-based inference
is plausible but lacks direct experimental support for GADD45B specifically
being required for differentiation. This may be an over-annotation based on
the gene name etymology rather than validated function.
action: MARK_AS_OVER_ANNOTATED
- term:
id: GO:0046330
label: positive regulation of JNK cascade
evidence_type: IEA
original_reference_id: GO_REF:0000117
review:
summary: >-
This is well-supported by experimental evidence. GADD45B activates MTK1/MEKK4
which in turn activates both p38 and JNK pathways [PMID:9827804]. However, GADD45B
also inhibits JNK via MKK7 binding in certain contexts [PMID:25314077], making
this context-dependent. The ARBA prediction is valid for the stress-responsive
pathway.
action: ACCEPT
supported_by:
- reference_id: PMID:9827804
supporting_text: "Expression of the GADD45-like genes induces p38/JNK activation\
\ and apoptosis"
- term:
id: GO:0051726
label: regulation of cell cycle
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: >-
Consistent with IBA annotation. InterPro-based inference supports known
GADD45 family function in cell cycle regulation via CRIF1 interaction [PMID:12716909].
action: KEEP_AS_NON_CORE
supported_by:
- reference_id: PMID:12716909
supporting_text: "CRIF1 binds specifically to the Gadd45 family proteins"
- term:
id: GO:1900745
label: positive regulation of p38MAPK cascade
evidence_type: IEA
original_reference_id: GO_REF:0000117
review:
summary: >-
This is strongly supported by experimental evidence. GADD45B activates MTK1/MEKK4
which activates MKK6, leading to p38 activation [PMID:9827804, PMID:12052864].
ARBA prediction is accurate.
action: ACCEPT
supported_by:
- reference_id: PMID:12052864
supporting_text: "GADD45 proteins bind a site in MTK1 near the inhibitory domain\
\ and relieve autoinhibition"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:12052864
review:
summary: >-
The vague term 'protein binding' should be replaced with a more specific MF
term.
This paper shows GADD45B binds MTK1/MEKK4 (a MAPKKK) and activates its kinase
activity. MTK1/MEKK4 is a MAPKKK (MAP3K4).
action: MODIFY
proposed_replacement_terms:
- id: GO:0031435
label: mitogen-activated protein kinase kinase kinase binding
supported_by:
- reference_id: PMID:12052864
supporting_text: "By a functional complementation screening with yeast cells,\
\ GADD45 proteins (GADD45alpha, beta, and gamma) were identified as MTK1 activators.\
\ GADD45 proteins bind a site in MTK1 near the inhibitory domain and relieve\
\ autoinhibition"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:16256071
review:
summary: >-
This paper shows CIN85 regulates MEKK4 activation by GADD45 proteins. The protein
binding annotation is too vague - this involves the MTK1/MEKK4 activation pathway.
action: MODIFY
proposed_replacement_terms:
- id: GO:0031435
label: mitogen-activated protein kinase kinase kinase binding
supported_by:
- reference_id: PMID:16256071
supporting_text: "CIN85 was also shown to regulate the activation of MEKK4 by\
\ GADD45 proteins and promote multi-ubiquitination of MEKK4"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:25314077
review:
summary: >-
This paper shows GADD45B binds directly to MKK7 and blocks its catalytic activity.
MKK7 is a MAPKK (MAP2K7). Should be annotated to a more specific term.
action: MODIFY
proposed_replacement_terms:
- id: GO:0031434
label: mitogen-activated protein kinase kinase binding
supported_by:
- reference_id: PMID:25314077
supporting_text: "GADD45β inhibits apoptosis by suppressing JNK signaling. It\
\ mediates this function by binding to the JNK kinase MKK7 and blocking its\
\ enzymatic activity by engaging the kinase catalytic pocket"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:32296183
review:
summary: >-
This is a large-scale binary protein interactome study (HuRI). Generic 'protein
binding' from high-throughput studies is not informative without mechanistic
context.
action: REMOVE
reason: >-
High-throughput interactome study. Specific interactions should be curated from
focused literature with mechanistic context rather than generic protein binding.
supported_by:
- reference_id: PMID:32296183
supporting_text: "Here we present a human 'all-by-all' reference interactome\
\ map of human binary protein interactions, or 'HuRI'. With approximately\
\ 53,000 protein-protein interactions, HuRI has approximately four times as\
\ many such interactions as there are high-quality curated interactions from\
\ small-scale studies"
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:33961781
review:
summary: >-
This is BioPlex 3.0, another large-scale protein interactome study. Same rationale
as PMID:32296183 - generic protein binding from HT studies is not informative.
action: REMOVE
reason: >-
High-throughput interactome study. Specific interactions should be curated from
focused literature with mechanistic context.
supported_by:
- reference_id: PMID:33961781
supporting_text: "Through affinity-purification mass spectrometry, we have created\
\ two proteome-scale, cell-line-specific interaction networks. The first,\
\ BioPlex 3.0, results from affinity purification of 10,128 human proteins-half\
\ the proteome-in 293T cells and includes 118,162 interactions among 14,586\
\ proteins"
- term:
id: GO:0005634
label: nucleus
evidence_type: IDA
original_reference_id: PMID:9827804
review:
summary: >-
Direct experimental evidence for nuclear localization. This is a core localization
for GADD45B's function in stress response signaling.
action: ACCEPT
supported_by:
- reference_id: PMID:9827804
supporting_text: "Using a yeast two-hybrid method, three related proteins, GADD45alpha\
\ (= GADD45), GADD45, (= MyD118), and GADD45gamma, were identified that bound\
\ to an N-terminal domain of MTK1"
- term:
id: GO:0005737
label: cytoplasm
evidence_type: IDA
original_reference_id: PMID:9827804
review:
summary: >-
Direct experimental evidence for cytoplasmic localization. GADD45B is found
in
both nucleus and cytoplasm, consistent with its role in signaling between
cellular compartments.
action: ACCEPT
supported_by:
- reference_id: PMID:9827804
supporting_text: "These proteins activated MTK1 kinase activity, both in vivo\
\ and in vitro"
- term:
id: GO:0043065
label: positive regulation of apoptotic process
evidence_type: IDA
original_reference_id: PMID:9827804
review:
summary: >-
Well-supported by experimental evidence showing expression of GADD45-like genes
induces p38/JNK activation and apoptosis. This reflects GADD45B's pro-apoptotic
activity through MTK1/MEKK4 activation in response to stress.
action: ACCEPT
supported_by:
- reference_id: PMID:9827804
supporting_text: "Expression of the GADD45-like genes induces p38/JNK activation\
\ and apoptosis, which can be partially suppressed by coexpression of a dominant\
\ inhibitory MTK1 mutant protein"
- term:
id: GO:0046330
label: positive regulation of JNK cascade
evidence_type: IDA
original_reference_id: PMID:9827804
review:
summary: >-
Well-supported by direct experimental evidence showing GADD45-like proteins
mediate activation of the p38/JNK pathway via MTK1/MEKK4. This is a core function.
action: ACCEPT
supported_by:
- reference_id: PMID:9827804
supporting_text: "Expression of the GADD45-like genes induces p38/JNK activation\
\ and apoptosis"
- term:
id: GO:1900745
label: positive regulation of p38MAPK cascade
evidence_type: IDA
original_reference_id: PMID:9827804
review:
summary: >-
Well-supported by direct experimental evidence [PMID:9827804]. Activation of
MTK1/MEKK4 by GADD45B leads to p38 MAPK activation. This is a core function.
action: ACCEPT
supported_by:
- reference_id: PMID:9827804
supporting_text: "The stress-responsive p38 and JNK MAPK pathways regulate cell\
\ cycle and apoptosis. A human MAPKKK, MTK1 (= MEKK4), mediates activation\
\ of both p38 and JNK in response to environmental stresses"
# NEW annotation for anti-apoptotic function via MKK7 inhibition
- term:
id: GO:0043066
label: negative regulation of apoptotic process
evidence_type: IDA
original_reference_id: PMID:25314077
review:
summary: >-
GADD45B suppresses JNK-mediated apoptosis by directly binding and inhibiting
MKK7.
This anti-apoptotic function is context-dependent, particularly relevant in
NF-kB-driven cancer cells like multiple myeloma.
action: NEW
supported_by:
- reference_id: PMID:25314077
supporting_text: "GADD45β suppresses JNK signaling and apoptosis by blocking\
\ MKK7 via direct physical interaction"
- reference_id: file:human/GADD45B/GADD45B-deep-research-perplexity.md
supporting_text: "GADD45B has also been identified as a promoter of cell survival\
\ through inhibition of JNK activation in multiple contexts"
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO
terms.
findings: []
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings: []
- id: GO_REF:0000117
title: Electronic Gene Ontology annotations created by ARBA machine learning models
findings: []
- id: PMID:9827804
title: A family of stress-inducible GADD45-like proteins mediate activation of the
stress-responsive MTK1/MEKK4 MAPKKK.
findings:
- statement: GADD45B (MyD118) binds to the N-terminal domain of MTK1 MAPKKK
supporting_text: three related proteins, GADD45alpha (= GADD45), GADD45, (= MyD118),
and GADD45gamma, were identified that bound to an N-terminal domain of MTK1
- statement: GADD45 proteins activate MTK1 kinase activity in vivo and in vitro
supporting_text: These proteins activated MTK1 kinase activity, both in vivo and
in vitro
- statement: GADD45B gene expression is induced by environmental stresses
supporting_text: The GADD45-like genes are induced by environmental stresses,
including MMS, UV, and gamma irradiation
- statement: GADD45-like genes induce p38/JNK activation and apoptosis
supporting_text: Expression of the GADD45-like genes induces p38/JNK activation
and apoptosis
- id: PMID:12052864
title: Regulation of MTK1/MEKK4 kinase activity by its N-terminal autoinhibitory
domain and GADD45 binding.
findings:
- statement: GADD45 proteins are specific activators of MTK1 MAPKKK
supporting_text: GADD45 proteins (GADD45alpha, beta, and gamma) were identified
as MTK1 activators
- statement: GADD45 proteins bind near the MTK1 inhibitory domain and relieve autoinhibition
supporting_text: GADD45 proteins bind a site in MTK1 near the inhibitory domain
and relieve autoinhibition
- statement: GADD45 binding eliminates inhibition of the kinase domain
supporting_text: Binding of GADD45 to the N-terminal region of MTK1 eliminates
inhibition of the kinase domain by the autoinhibitory domain
- id: PMID:16256071
title: CIN85 regulates the ability of MEKK4 to activate the p38 MAP kinase pathway.
findings:
- statement: CIN85 enhances MEKK4 activation of MKK6 and p38 following oxidative
stress
supporting_text: CIN85 binding to MEKK4 enhances the activation of MKK6 and of
the downstream p38 MAP kinase following oxidative stress and growth factor stimulation
- statement: CIN85 regulates the activation of MEKK4 by GADD45 proteins
supporting_text: CIN85 was also shown to regulate the activation of MEKK4 by GADD45
proteins
- id: PMID:25314077
title: Cancer-selective targeting of the NF-κB survival pathway with GADD45β/MKK7
inhibitors.
findings:
- statement: GADD45B is a transcriptional target of NF-κB that inhibits the JNK
pathway
supporting_text: we had previously identified the GADD45-family gene, GADD45B,
as a transcriptional target of NF-κB encoding a potent and selective inhibitor
of the JNK MAPK pathway
- statement: GADD45B suppresses JNK signaling by blocking MKK7 via direct interaction
supporting_text: GADD45β suppresses JNK signaling and apoptosis by blocking MKK7
via direct physical interaction
- statement: GADD45B is highly expressed in multiple myeloma
supporting_text: GADD45B was markedly upregulated in monoclonal CD138+ PCs from
MM patients
- statement: GADD45β promotes survival of MM cells by inhibiting JNK-mediated apoptosis
supporting_text: Hence, GADD45β promotes the survival of MM cells by inhibiting
JNK-mediated apoptosis
- id: PMID:12716909
title: CR6-interacting factor 1 interacts with Gadd45 family proteins and modulates
the cell cycle.
findings:
- statement: CRIF1 binds specifically to GADD45 family proteins including GADD45B
supporting_text: CRIF1 binds specifically to the Gadd45 family proteins
- statement: CRIF1 inhibits Cdc2-cyclin B1 and Cdk2-cyclin E with additive effects
with GADD45
supporting_text: Recombinant CRIF1 inhibits the histone H1 kinase activity of
immunoprecipitated Cdc2-cyclin B1 and Cdk2-cyclin E, and the inhibitory effects
were additive with Gadd45 proteins
- id: PMID:32296183
title: A reference map of the human binary protein interactome.
findings: []
- id: PMID:33961781
title: Dual proteome-scale networks reveal cell-specific remodeling of the human
interactome.
findings: []
core_functions:
- description: Binds to MTK1/MEKK4 (MAP3K4) N-terminal regulatory domain, relieving
autoinhibition and activating downstream p38 and JNK MAPK pathways in response
to environmental stress.
molecular_function:
id: GO:0031435
label: mitogen-activated protein kinase kinase kinase binding
directly_involved_in:
- id: GO:1900745
label: positive regulation of p38MAPK cascade
- id: GO:0046330
label: positive regulation of JNK cascade
locations:
- id: GO:0005737
label: cytoplasm
- id: GO:0005634
label: nucleus
supported_by:
- reference_id: PMID:9827804
supporting_text: These proteins activated MTK1 kinase activity, both in vivo and
in vitro
- reference_id: PMID:12052864
supporting_text: GADD45 proteins bind a site in MTK1 near the inhibitory domain
and relieve autoinhibition.
- reference_id: file:human/GADD45B/GADD45B-deep-research-perplexity.md
supporting_text: "Upon stress stimulation, GADD45B binds to MTK1/MEKK4, enhancing\
\ the autophosphorylation and kinase activity of this upstream regulator, which\
\ subsequently leads to phosphorylation and activation of downstream p38 and\
\ JNK kinases"
- description: Binds directly to MKK7 (MAP2K7) and blocks its kinase activity, suppressing
JNK-mediated apoptosis. This anti-apoptotic function is particularly relevant
in cancer contexts where GADD45B acts downstream of NF-kB.
molecular_function:
id: GO:0031434
label: mitogen-activated protein kinase kinase binding
directly_involved_in:
- id: GO:0043066
label: negative regulation of apoptotic process
locations:
- id: GO:0005737
label: cytoplasm
supported_by:
- reference_id: PMID:25314077
supporting_text: The percentages of apoptotic cells are depicted.See also Figure
S2.Development of D-Tetrapeptide Inhibitors of the GADD45β/MKK7 ComplexGiven
the essential antiapoptotic role of GADD45β in MM and our previous results showing
that GADD45β suppresses JNK signaling and apoptosis by blocking MKK7 via direct
physical interaction (De Smaele et al., 2001, Papa et al., 2004, Papa et al.,
2007), we aimed to develop selective inhibitors of this protein-protein interaction
in order to induce cytotoxic JNK signaling in MM cells
- reference_id: file:human/GADD45B/GADD45B-deep-research-perplexity.md
supporting_text: "GADD45B directly binds to MKK7 and inhibits its catalytic activity\
\ toward JNK substrates, providing a mechanism through which GADD45B can attenuate\
\ JNK signaling in specific cellular contexts"
proposed_new_terms: []
suggested_questions:
- question: >-
How is the switch between GADD45B's pro-apoptotic function (MTK1/MEKK4 activation)
and anti-apoptotic function (MKK7 inhibition) regulated in different cellular
contexts?
experts: []
- question: >-
What is the structural basis for GADD45B's selective inhibition of MKK7 versus
its
activation of MTK1/MEKK4?
experts: []
suggested_experiments:
- experiment_type: protein structure
description: >-
Solve the structure of GADD45B in complex with MTK1 and separately with MKK7 to
understand the molecular basis for its opposing effects on these two kinases.
- experiment_type: functional assay
description: >-
Determine the relative binding affinities of GADD45B for MTK1 versus MKK7 and
how
these are modulated by NF-kB pathway activation.