GBX2 is a nuclear homeobox transcription factor that binds sequence-specific cis-regulatory DNA and regulates RNA polymerase II transcription. Direct human-cell experiments show GBX2 occupancy and binding at target regulatory regions, nuclear localization, and transcriptional activation through an EEF1A1 promoter element; developmental studies also support context-dependent transcriptional repression. During vertebrate embryogenesis, spatially restricted Gbx2 activity specifies anterior hindbrain identity by opposing Otx2, positions and maintains the midbrain-hindbrain isthmic organizer, and supports patterning of rhombomere 1-derived cerebellar territory and other nervous-system structures. Human GBX2 transcript is detected in the developing CNS, while the causal developmental assignments derive primarily from conserved model-organism loss- and gain-of-function studies.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000981 DNA-binding transcription factor activity, RNA polymerase II-specific | IBA GO_REF:0000033 | ACCEPT | Summary: GBX2 is a homeodomain transcription factor that binds regulatory DNA and controls RNA polymerase II transcription. Phylogenetic inference agrees with direct human-cell ChIP, gel-shift, and reporter evidence. Reason: This direction-neutral transcription-factor term best captures the core molecular activity because GBX2 can activate or repress transcription depending on regulatory sequence and cofactors. Supporting Evidence: PMID:23144817 We show through gel shift analyses that sequences within the promoter or introns of EEF1A1, ROBO1, PCDH15, USH2A and NOTCH2, are directly bound by GBX2. |
| GO:0006357 regulation of transcription by RNA polymerase II | IBA GO_REF:0000033 | ACCEPT | Summary: Direct GBX2 promoter-binding and reporter experiments establish regulation of RNA polymerase II transcription. Reason: This is the biological-process counterpart of GBX2's core DNA-binding transcription-factor activity and is appropriately direction-neutral. Supporting Evidence: PMID:23144817 Furthermore, we show that GBX2 activates transcriptional activity through the promoter of EEF1A1 |
| GO:0000977 RNA polymerase II transcription regulatory region sequence-specific DNA binding | IBA GO_REF:0000033 | ACCEPT | Summary: GBX2 occupies cis-regulatory regions in human cells and directly binds promoter and intronic target sequences in gel-shift assays. Reason: This specific DNA-binding term accurately describes the homeodomain-mediated recognition of RNA polymerase II regulatory regions. Supporting Evidence: PMID:23144817 We show through gel shift analyses that sequences within the promoter or introns of EEF1A1, ROBO1, PCDH15, USH2A and NOTCH2, are directly bound by GBX2. |
| GO:0005634 nucleus | IBA GO_REF:0000033 | ACCEPT | Summary: GBX2 functions in the nucleus, where it binds chromatin and regulates transcription; expressed GBX2 fusion protein was observed in nuclei of human cells. Reason: Nucleus is the active compartment for GBX2's core transcription-factor activity. Supporting Evidence: PMID:23144817 Merge displays nuclear localization of GFP-GBX2 fusion proteins. |
| GO:0051960 regulation of nervous system development | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Gbx2 regulates anterior-hindbrain identity, midbrain-hindbrain organizer position, and cerebellar patterning in vertebrate developmental models. Reason: The annotation is biologically well supported and is a principal developmental output, but it is a tissue- and stage-specific context of the core nuclear transcription-factor activity rather than a separate molecular function. Supporting Evidence: PMID:10490024 We propose that formation of a normal MHB organizer depends on a sharp Otx2 caudal border and that Gbx2 is required to position and sharpen this border. PMID:12367504 Mid/hindbrain organizer gene expression, however, continues to be dependent on Gbx2. |
| GO:0000981 DNA-binding transcription factor activity, RNA polymerase II-specific | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro mapping from the conserved homeobox is consistent with direct GBX2 DNA-binding and transcriptional-regulation experiments. Reason: The electronic inference is correct and independently corroborated by direct human-cell evidence. Supporting Evidence: PMID:23144817 Gbx2 encodes a DNA-binding transcription factor that plays pivotal roles during embryogenesis. |
| GO:0003677 DNA binding | IEA GO_REF:0000002 | MODIFY | Summary: GBX2 binds DNA through its homeodomain, but the root-level DNA-binding term omits experimentally established sequence and regulatory-region specificity. Reason: Replace this uninformative parent term with the more specific RNA polymerase II regulatory-region sequence-specific DNA-binding activity already supported for GBX2. Proposed replacements: RNA polymerase II transcription regulatory region sequence-specific DNA binding Supporting Evidence: PMID:23144817 We show through gel shift analyses that sequences within the promoter or introns of EEF1A1, ROBO1, PCDH15, USH2A and NOTCH2, are directly bound by GBX2. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping to nucleus agrees with direct localization and GBX2's transcription-factor mechanism. Reason: The electronic localization is correct and experimentally corroborated. Supporting Evidence: PMID:23144817 Merge displays nuclear localization of GFP-GBX2 fusion proteins. |
| GO:0006355 regulation of DNA-templated transcription | IEA GO_REF:0000002 | MODIFY | Summary: GBX2 regulates DNA-templated transcription, but the generic parent term loses the experimentally supported RNA polymerase II context. Reason: Use the more informative RNA polymerase II-specific process term supported by GBX2 promoter and reporter experiments. Proposed replacements: regulation of transcription by RNA polymerase II Supporting Evidence: PMID:23144817 Furthermore, we show that GBX2 activates transcriptional activity through the promoter of EEF1A1 |
| GO:0045944 positive regulation of transcription by RNA polymerase II | IEA GO_REF:0000108 | ACCEPT | Summary: This logical inference from transcription-activator activity is supported by direct activation of an EEF1A1 promoter reporter by GBX2. Reason: Positive transcriptional regulation is a genuine context-dependent GBX2 output, even though GBX2 can repress other targets and should not be described as exclusively activating. Supporting Evidence: PMID:23144817 Furthermore, we show that GBX2 activates transcriptional activity through the promoter of EEF1A1 |
| GO:0001228 DNA-binding transcription activator activity, RNA polymerase II-specific | IEA GO_REF:0000107 | ACCEPT | Summary: Orthology transfer of transcription-activator activity is corroborated by human-cell GBX2 promoter-binding and reporter activation evidence. Reason: The activity is experimentally supported for an EEF1A1 promoter context. It is retained as one direction-specific mode within GBX2's broader context-dependent transcriptional role. Supporting Evidence: PMID:23144817 In contrast, our results here show that GBX2 functions as a transcriptional activator of the EEF1A1 gene. |
| GO:1990837 sequence-specific double-stranded DNA binding | IDA PMID:28473536 Impact of cytosine methylation on DNA binding specificities ... | ACCEPT | Summary: The GBX2 GOA row derives from a large methylation-sensitive SELEX survey and is consistent with independent GBX2 gel-shift and chromatin-occupancy experiments. Reason: Sequence-specific double-stranded DNA binding is a core homeodomain function. The GBX2-specific supplementary result is accepted in deference to the experimental curator and is independently corroborated by direct GBX2 binding assays. Supporting Evidence: PMID:28473536 By analysis of 542 human TFs with methylation-sensitive SELEX (systematic evolution of ligands by exponential enrichment) PMID:23144817 We show through gel shift analyses that sequences within the promoter or introns of EEF1A1, ROBO1, PCDH15, USH2A and NOTCH2, are directly bound by GBX2. |
| GO:0000785 chromatin | ISA GO_REF:0000113 | ACCEPT | Summary: TFClass-based chromatin localization agrees with direct ChIP-seq evidence that GBX2 occupies genomic regulatory regions in human cells. Reason: Chromatin is an appropriate active location for a sequence-specific transcription factor with demonstrated genomic occupancy. Supporting Evidence: PMID:23144817 Using chromatin immunoprecipitation coupled with direct sequencing (ChIP-Seq) analysis in a human prostate cancer cell line, we identified cis-regulatory elements bound by GBX2 to provide insight into its direct downstream targets. |
| GO:0000981 DNA-binding transcription factor activity, RNA polymerase II-specific | ISA GO_REF:0000113 | ACCEPT | Summary: TFClass assignment as a sequence-specific DNA-binding transcription factor is consistent with the GBX2 homeodomain and direct human-cell binding and transcription assays. Reason: This is the core molecular activity and is independently supported beyond the similarity inference. Supporting Evidence: PMID:23144817 Gbx2 encodes a DNA-binding transcription factor that plays pivotal roles during embryogenesis. |
| GO:0003700 DNA-binding transcription factor activity | TAS PMID:9346236 The homeobox gene GBX2, a target of the myb oncogene, mediat... | ACCEPT | Summary: The original TAS paper is abstract-only locally, so its precise transcription assay cannot be rechecked. The annotation itself is strongly corroborated by later direct GBX2 DNA-binding, ChIP, and reporter experiments. Reason: The broad transcription-factor term is correct. Acceptance relies on the complete evidence synthesis and defers to the original curator rather than treating unavailable full text as contrary evidence. Supporting Evidence: PMID:23144817 Gbx2 encodes a DNA-binding transcription factor that plays pivotal roles during embryogenesis. |
| GO:0007399 nervous system development | TAS PMID:8838315 Characterization and sequence analysis of the human homeobox... | KEEP AS NON CORE | Summary: The original human cloning paper establishes developing-CNS expression but its cached abstract does not provide a causal developmental assay. Conserved mouse genetic studies strongly support the broader nervous-system-development role. Reason: Retain the biologically correct developmental annotation while marking it as a context-specific output. Full text for the original TAS source is unavailable, so the curator is not overruled; causal support comes from additional vertebrate studies. Supporting Evidence: PMID:8838315 A single 2.2-kb transcript was detected by Northern analysis in the developing human CNS as well as in other tissues. PMID:21266408 Without Gbx2, hindbrain-born cells abnormally populate the entire midbrain, demonstrating that Gbx2 is essential for specifying hindbrain fate. |
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Download this section (compressed HTML)Q: Which cofactors and regulatory-element features switch GBX2 between transcriptional activation and repression in human neural progenitors?
Q: Which human GBX2-bound targets directly implement anterior-hindbrain identity and isthmic-organizer maintenance, and which model-organism targets are conserved in human cells?
Experiment: Generate inducible GBX2 knockout and rescue lines in human pluripotent-stem-cell-derived midbrain-hindbrain boundary or cerebellar organoid models. Combine time-resolved single-cell RNA-seq with GBX2 CUT&RUN to distinguish direct transcriptional targets from secondary patterning effects and test effects on OTX2, FGF8, WNT1, and lineage-boundary programs.
Hypothesis: GBX2 directly establishes anterior-hindbrain transcriptional identity and organizer-adjacent signaling programs in human neural progenitors.
Type: Human neural-patterning perturbation with multi-omic profiling
Experiment: Test wild-type and homeodomain- or EH1-motif-mutant GBX2 across endogenous target enhancers using reporter assays, cofactor perturbations, occupancy measurements, and nascent-transcription readouts in matched neural progenitors.
Hypothesis: GBX2 target directionality is determined by regulatory sequence and recruitment of activating versus TLE/Groucho-family repressive cofactors.
Type: Cofactor-dependent promoter and enhancer assay
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