Tetratricopeptide repeat protein 28 (TTC28/TPRBK), a very large (~271 kDa, ~2365-2481 AA) protein built from ~25-28 tetratricopeptide repeat (TPR) motifs. TPR domains are helical repeat motifs that mediate protein-protein interactions, and TTC28 acts as a scaffold/adaptor rather than an enzyme. Mechanistic work (Zhang et al. 2024, PNAS) establishes that TTC28 is a substrate of HSPA8/HSC70 chaperone-mediated autophagy (CMA)/microautophagy: its TPR domains bind the C-terminal PTIEEVD motif of HSPA8, and it carries multiple KFERQ-like motifs, leading to LAMP2A-dependent lysosomal turnover. Functionally, TTC28 is required for the maintenance of chromosomal stability, acting through regulation of mitosis and cytokinesis. It is mainly cytoplasmic with perinuclear enrichment and localizes to mitotic structures including the midbody and spindle apparatus, where it colocalizes with beta-tubulin (TUBB) and partially overlaps Aurora B (AURKB). Loss of TTC28 increases micronuclei frequency and DNA-damage markers (gamma-H2AX, comet assay), and TTC28 is frequently mutated/down-regulated in cancers where its loss may contribute to chromosomal instability (CIN).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000922 spindle pole | IEA GO_REF:0000044 | ACCEPT | Summary: Phylogenetic inference for spindle pole localization. TTC28 concentrates at spindle poles during mitosis. Reason: Core localization confirmed by IDA (PMID:23036704). Supporting Evidence: file:human/TTC28/TTC28-deep-research-falcon.md Detectable in mitotic structures including the **midbody**, consistent with involvement in cytokinesis. |
| GO:0005813 centrosome | IEA GO_REF:0000044 | ACCEPT | Summary: Subcellular location annotation for centrosome. TTC28 localizes to centrosomes throughout cell cycle. Reason: Well-established centrosomal localization. |
| GO:0005819 spindle | IEA GO_REF:0000044 | ACCEPT | Summary: Subcellular location annotation for spindle. TTC28 localizes to mitotic spindle structures, consistent with falcon deep research reporting perinuclear/midbody localization and TUBB colocalization. Reason: Consistent with spindle pole localization and microtubule association. Supporting Evidence: file:human/TTC28/TTC28-deep-research-falcon.md Proteomics identified **TUBB (Ξ²-tubulin)** as a TTC28-binding candidate, and confocal microscopy shows **TTC28/TUBB colocalization** in the perinuclear cytoplasm and **midbody**. |
| GO:0005856 cytoskeleton | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: Broad cytoskeleton term. TTC28 associates with microtubule cytoskeleton structures and perturbs tubulin gene expression on loss. Reason: Too general. More specific spindle/centrosome/midbody terms preferred, but microtubule association is supported. Supporting Evidence: file:human/TTC28/TTC28-deep-research-falcon.md TTC28 knockout perturbs expression of tubulin-related genes (e.g., **TUBB6, TUBA1A, TTL**), reinforcing a functional link to microtubule dynamics. |
| GO:0030496 midbody | IEA GO_REF:0000044 | ACCEPT | Summary: Duplicate midbody annotation with IEA evidence. Reason: Consistent midbody localization. |
| GO:0051301 cell division | IEA GO_REF:0000043 | ACCEPT | Summary: Cell division process. TTC28 functions in mitosis/cytokinesis. Reason: Core biological process. Supporting Evidence: file:human/TTC28/TTC28-deep-research-falcon.md supports **high-fidelity mitosis/cytokinesis** and thereby reduces **chromosomal instability** |
| GO:0030496 midbody | IDA PMID:23036704 A novel big protein TPRBK possessing 25 units of TPR motif i... | ACCEPT | Summary: Direct assay evidence for midbody localization from key paper. TTC28 concentrates at midbody during cytokinesis. Independently confirmed by falcon deep research (Zhang 2024 confocal imaging). Reason: Experimental evidence from PMID:23036704, core localization. Supporting Evidence: PMID:23036704 Oct 1. A novel big protein TPRBK possessing 25 units of TPR motif is essential for the progress of mitosis and cytokinesis. file:human/TTC28/TTC28-deep-research-falcon.md Detectable in mitotic structures including the **midbody**, consistent with involvement in cytokinesis. |
| GO:0007346 regulation of mitotic cell cycle | IMP PMID:23036704 A novel big protein TPRBK possessing 25 units of TPR motif i... | ACCEPT | Summary: Mutant phenotype evidence for regulation of mitotic cell cycle. TTC28 depletion disrupts cell division progression. Falcon deep research (Zhang 2024) reinforces a mitosis/cytokinesis regulatory role required for chromosomal stability. Reason: Experimental evidence from PMID:23036704, core biological process. Supporting Evidence: PMID:23036704 Oct 1. A novel big protein TPRBK possessing 25 units of TPR motif is essential for the progress of mitosis and cytokinesis. file:human/TTC28/TTC28-deep-research-falcon.md a large TPR scaffold/adaptor that couples chaperone/autophagy machinery to the fidelity of mitotic and cytokinetic processes, likely through protein interaction networks rather than enzymatic catalysis |
| GO:0019900 kinase binding | IPI PMID:23036704 A novel big protein TPRBK possessing 25 units of TPR motif i... | KEEP AS NON CORE | Summary: Kinase binding from protein interaction study. Falcon deep research (Zhang 2024) provides specific support: TTC28 partially overlaps and is linked to Aurora B kinase (AURKB) at mitotic structures, consistent with a TPR scaffold engaging a mitotic kinase. Note the best-supported molecular interaction is with the HSPA8/HSC70 chaperone (via its C-terminal PTIEEVD motif), which is an ATPase but is more precisely a chaperone-binding (CMA substrate) relationship than generic kinase binding. Reason: The kinase-binding annotation is plausible (AURKB association reported), but falcon evidence indicates the dominant, mechanistically defining interaction is HSPA8 chaperone binding driving CMA turnover, not a catalytic-kinase scaffolding function. Retained as non-core pending identification of the specific kinase(s) bound. Supporting Evidence: file:human/TTC28/TTC28-deep-research-falcon.md TTC28 shows **partial overlap** with **AURKB (Aurora B kinase)** |
| GO:0007049 cell cycle | IMP PMID:39630868 The essential role of TTC28 in maintaining chromosomal stabi... | NEW | Summary: NEW annotation grounded in Zhang et al. 2024 (PNAS): TTC28 is required for high-fidelity mitosis and cytokinesis, and its loss increases micronuclei frequency and DNA-damage markers, placing its activity within the cell cycle. Reason: Zhang et al. 2024 demonstrate by mutant/knockout phenotype (IMP) that loss of TTC28 increases micronuclei frequency ~3-fold and that TTC28 regulates mitosis and cytokinesis to maintain genome integrity. This supports the broader cell-cycle context; the more specific regulation of mitotic cell cycle term remains the core BP. Supporting Evidence: PMID:39630868 the baseline frequency of micronuclei (FMN) in human cancer cells with TTC28 knockout cells was three times greater than that in cells with wild-type TTC28 (7.7% vs. 2.3%, P = 4.86E-09). file:human/TTC28/TTC28-deep-research-falcon.md It reports cell-cycle regulation of TTC28 abundance and multiple genome instability readouts (micronuclei, Ξ³H2AX, comet assays). |
| GO:0030544 Hsp70 protein binding | IPI PMID:39630868 The essential role of TTC28 in maintaining chromosomal stabi... | NEW | Summary: NEW annotation from falcon deep research: TTC28 directly binds the HSPA8 (HSC70, an Hsp70-family chaperone) via its TPR domains engaging the HSPA8 C-terminal PTIEEVD motif. This is the best-supported molecular interaction of TTC28 and underlies its turnover by chaperone-mediated autophagy. Reason: Direct interaction with HSPA8 (an Hsp70-family member) demonstrated by Zhang et al. 2024 (PNAS) via CoIP/BiFC/mutant analysis; a TPR-PTIEEVD chaperone-binding mode. The specific Hsp70 protein binding term is more informative than the generic heat shock protein binding parent. Supporting Evidence: file:human/TTC28/TTC28-deep-research-falcon.md TTC28 **directly binds HSPA8** through the **HSPA8 C-terminal PTIEEVD motif** PMID:39630868 The tetratricopeptide repeat domains of TTC28 bind to the C-terminal motif (PTIEEVD) in HSPA8, resulting in the subsequent degradation of TTC28 via CMA/microautophagy. |
| GO:0061684 chaperone-mediated autophagy | IDA PMID:39630868 The essential role of TTC28 in maintaining chromosomal stabi... | NEW | Summary: NEW annotation from falcon deep research: TTC28 is a substrate of HSPA8/LAMP2A-dependent chaperone-mediated autophagy (CMA)/microautophagy and carries multiple KFERQ-like motifs. CMA control of TTC28 abundance is itself required for maintenance of genome stability. Reason: Established as a CMA substrate by Zhang et al. 2024 (PNAS); CMA-mediated TTC28 degradation is a master regulator of TTC28's genome-stability function. Supporting Evidence: file:human/TTC28/TTC28-deep-research-falcon.md TTC28 also contains **16 KFERQ-like motifs**, consistent with CMA targeting logic. PMID:39630868 the subsequent degradation of TTC28 via CMA/microautophagy. |
| GO:0005829 cytosol | IDA PMID:39630868 The essential role of TTC28 in maintaining chromosomal stabi... | NEW | Summary: NEW annotation from falcon deep research: TTC28 is mainly cytoplasmic with perinuclear enrichment, the compartment where it engages cytosolic chaperones (HSPA8) and mitotic/cytoskeletal machinery. Reason: Imaging/fractionation in human cancer cell lines shows predominantly cytoplasmic localization (Zhang et al. 2024, PNAS); consistent with cytosolic chaperone engagement. Supporting Evidence: file:human/TTC28/TTC28-deep-research-falcon.md Mainly cytoplasmic**, with **perinuclear enrichment** |
Loading supporting contentβ¦
Download this section (compressed HTML)Q: Which specific kinases bind TTC28 and how does this regulate mitosis?
Suggested experts: Cell cycle researchers
Q: Is TTC28's role in chromosomal stability mediated mainly through its own scaffolding activity at the midbody/spindle, or indirectly through CMA-controlled turnover of its abundance?
Suggested experts: Autophagy researchers, Cell cycle researchers
Experiment: Co-IP and mass spec to identify TTC28-binding kinases
Hypothesis: TTC28 scaffolds mitotic kinases
Type: proteomics
Experiment: Separation-of-function mutants disrupting the TPR-PTIEEVD (HSPA8) interface vs. midbody localization, assayed for micronuclei frequency, to dissect whether CMA targeting or mitotic scaffolding is the primary driver of chromosomal stability.
Hypothesis: Mitotic scaffolding by TTC28 maintains chromosomal stability independently of its CMA-mediated turnover.
Type: mutational_analysis
Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)