G-box-binding factor (GBF) is a developmentally regulated, highly basic zinc-finger transcription factor of Dictyostelium discoideum. It contains two zinc-finger motifs and binds sequence-specifically to G-box / CA-rich regulatory elements (CAEs) found in the promoters of cell-type-specific late (post-aggregative) genes, including prestalk and prespore genes. GBF acts in the nucleus as a cAMP-responsive transcriptional activator that, in response to the high, continuous extracellular cAMP accumulating after aggregation, drives induction of the late-gene program marking the developmental switch from the loose aggregate to multicellular morphogenesis. GBF is essential for this switch; cells lacking GBF arrest at the loose-mound stage, fail to induce cell-type-specific genes, and cannot establish a dominant signaling center or form a tip. GBF thus sits at the top of the transcriptional hierarchy controlling the transition from aggregation to cell differentiation and fruiting body (sorocarp) formation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: Nuclear localization inferred from the UniProt subcellular location vocabulary. This is correct and independently supported by direct experimental evidence for GBF, consistent with its role as a DNA-binding transcription factor that acts in the nucleus. Reason: GBF is a nuclear transcription factor. The IEA/UniProt localization matches direct experimental evidence (IDA) for nuclear localization of the same gene product and is consistent with its DNA-binding activity. Supporting Evidence: PMID:8065317 in vitro-transcribed and -translated GBF binds all three SP60/cotC CAEs in a sequence-specific manner |
| GO:0009642 response to light intensity | HEP PMID:41057014 Transcriptomic and metabolomic insights into light-mediated ... | KEEP AS NON CORE | Summary: This annotation derives from a high-throughput expression profiling study in which gbfA transcript levels changed with light exposure (gbfA was downregulated in the dark during the unicellular phase). This reflects that gbfA expression is modulated under different light conditions, not a dedicated molecular role of GBF in a light-response pathway. It is a peripheral, expression-based observation rather than a core function. Reason: The evidence is a differential-expression signal from a transcriptomic screen, capturing that gbfA responds to (or is co-regulated with) light-mediated developmental changes. GBF's core function is transcriptional activation of late genes; light responsiveness of its transcript is a downstream/contextual observation, so this is retained as non-core. Supporting Evidence: PMID:41057014 G-box binding factor GbfA and TgrC1 (lagC) have also reported to be involved in the post-aggregation stage [42], both of which were downregulated under the dark condition from transcriptomic analysis in the unicellular phase. |
| GO:0110013 positive regulation of aggregation involved in sorocarp development | IMP PMID:8125261 Cloning and characterization of the G-box binding factor, an... | KEEP AS NON CORE | Summary: GBF-null cells arrest at the loose aggregate stage and fail to make the transition to multicellular morphogenesis. GBF is required for the post-aggregative developmental program. This is a valid developmental-process annotation but reflects the downstream consequence of GBF's transcriptional activity rather than its molecular function. Reason: The gene-disruption phenotype (developmental arrest at the loose aggregate stage) supports GBF's role in the aggregation-to-morphogenesis switch. This is a genuine developmental requirement but is a downstream effect of its core transcription-factor activity, so it is kept as non-core. Supporting Evidence: PMID:8125261 Disruption of the GBF gene by homologous recombination results in the loss of all GBF DNA-binding activity, developmental arrest at the loose aggregate stage, and the loss of late gene induction during development or in response to extracellular cAMP. |
| GO:0140582 adenylate cyclase-activating G protein-coupled cAMP receptor signaling pathway | IMP PMID:9698452 lagC-null and gbf-null cells define key steps in the morphog... | KEEP AS NON CORE | Summary: gbf-null mounds fail to establish a single dominant cAMP signaling-wave center and cannot make the morphogenetic transition from random to rotational cell motion. This places GBF upstream of (or within) the cAMP-receptor signaling program during mound morphogenesis, but the effect is an indirect consequence of GBF's requirement for late-gene induction rather than a direct role in the receptor pathway itself. Reason: The IMP evidence shows a signaling-center defect in gbf-null mounds, but this is downstream of GBF-driven transcription of post-aggregative genes (e.g. lagC/tgrC1). It is a real developmental phenotype worth retaining but is not GBF's core molecular function. Supporting Evidence: PMID:9698452 One reason for this was the inability of the mutant mounds to establish a single, dominant signaling-wave center. PMID:9698452 lagC-null and gbf-null cells fail to induce cell-type-specific genes ordinarily expressed during multicellular development. |
| GO:0030587 sorocarp development | IEP PMID:25887420 Leaps and lulls in the developmental transcriptome of Dictyo... | KEEP AS NON CORE | Summary: Based on the developmental expression profile, gbfA is expressed during the transition from aggregates to mounds, consistent with its established role in sorocarp (fruiting body) development. This expression-based annotation is correct in placing GBF in the developmental program but is a broad, non-core process term. Reason: The IEP evidence is an expression-pattern correlation identifying gbfA as a transition-stage transcription factor. Sorocarp development is a valid but general developmental annotation, downstream of GBF's core transcriptional activity, so it is kept as non-core. Supporting Evidence: PMID:25887420 Two transcription factors involved in the transition from aggregates to mounds, gbfA and comH [29,30], also displayed temporally consistent expression between treatments |
| GO:0043565 sequence-specific DNA binding | IDA PMID:19757394 Identification of a target for CudA, the transcription facto... | ACCEPT | Summary: GBF is a zinc-finger transcription factor that binds sequence-specific G-box / CA-rich elements in target promoters. Sequence-specific DNA binding is a core molecular function of GBF, directly demonstrated for defined regulatory elements. Reason: Sequence-specific DNA binding to G-boxes / CAEs is directly demonstrated for GBF and is central to its role as a transcriptional activator. This is a core molecular-function annotation. Supporting Evidence: PMID:19757394 a zinc finger transcription factor. There are potential GBF binding sites PMID:8065317 in vitro-transcribed and -translated GBF binds all three SP60/cotC CAEs in a sequence-specific manner |
| GO:1902168 response to catechin | IDA PMID:23516620 The green tea catechin epigallocatechin gallate (EGCG) block... | KEEP AS NON CORE | Summary: In this study, the green tea catechin EGCG delayed development, and expression of late-aggregate/early-mound genes including gbfA was delayed by 4-6 h. This is an indirect, expression-based observation (gbfA transcript timing shifts when development is pharmacologically delayed) rather than a dedicated GBF role in catechin response. Reason: The evidence is that catechin (EGCG) treatment delays gbfA expression as part of a general developmental delay, not that GBF has a specific molecular function in responding to catechin. This is a peripheral, context-dependent annotation retained as non-core. Supporting Evidence: PMID:23516620 The delays in expression were also observed for tgrC and gbfA, genes expressed from late aggregate to early mound stage |
| GO:0048102 autophagic cell death | IMP PMID:19133302 Autophagic cell death: analysis in Dictyostelium. | KEEP AS NON CORE | Summary: GbfA is one of several genes whose mutation was used to genetically dissect autophagic cell death (ACD) in Dictyostelium, helping to dissociate vacuolisation from cell death. This connects GBF to the ACD program, but the relationship is indirect - GBF is required for the developmental (late-gene) context in which ACD is studied rather than being a dedicated cell-death effector. Reason: The cited review reports GbfA among genes mutated to dissect ACD features. This is a developmental/genetic-dissection context rather than a core molecular function of GBF, so it is kept as non-core. Supporting Evidence: PMID:19133302 These mutations allowed the genetic dissection of ACD features, dissociating in particular vacuolisation from cell death. |
| GO:0030587 sorocarp development | HMP PMID:17659086 High-throughput analysis of spatio-temporal dynamics in Dict... | KEEP AS NON CORE | Summary: High-throughput mutant-phenotype screen placing gbfA among genes required for normal fruiting body (sorocarp) development. This is consistent with the well-established developmental-arrest phenotype of GBF-null cells but is a broad developmental-process annotation. Reason: The HMP evidence supports a developmental requirement for gbfA, corroborating the loose-aggregate arrest seen in targeted knockouts. Sorocarp development is a valid but general annotation downstream of GBF's core transcriptional function, so it is retained as non-core. Supporting Evidence: PMID:8125261 developmental arrest at the loose aggregate stage |
| GO:0003677 DNA binding | IDA PMID:8065317 A GBF-binding site and a novel AT element define the minimal... | MODIFY | Summary: GBF directly binds DNA regulatory elements (the SP60/cotC CAEs). DNA binding is correct and core, but the more specific child term sequence-specific DNA binding (already annotated separately) better captures the demonstrated activity. Reason: The direct binding demonstrated is sequence-specific binding to defined CA-rich / G-box elements, so the more informative child term GO:0043565 sequence-specific DNA binding is preferable to the general parent GO:0003677. Proposed replacements: sequence-specific DNA binding Supporting Evidence: PMID:8065317 in vitro-transcribed and -translated GBF binds all three SP60/cotC CAEs in a sequence-specific manner |
| GO:0003700 DNA-binding transcription factor activity | IMP PMID:8125261 Cloning and characterization of the G-box binding factor, an... | ACCEPT | Summary: GBF is a cAMP-responsive transcriptional activator required for induction of cell-type-specific late genes. DNA-binding transcription factor activity is the core molecular function of GBF. Reason: Gene disruption abolishes late-gene induction and constitutive GBF expression restores rapid cAMP-induced late-gene activation, demonstrating GBF acts as a transcriptional activator. This is the core molecular function. Supporting Evidence: PMID:8125261 Constitutive expression of GBF complements the null phenotype and allows for the rapid activation of a class of late genes in response to cAMP. PMID:8125261 GBF acts as an extracellular cAMP-responsive transcriptional activator regulating late gene expression and is an essential component of a developmental switch between aggregation and cellular morphogenesis |
| GO:0005634 nucleus | IDA PMID:8125261 Cloning and characterization of the G-box binding factor, an... | ACCEPT | Summary: Direct evidence localizes GBF to the nucleus, consistent with its function as a DNA-binding transcription factor. This is a core localization. Reason: Nuclear localization is directly supported and consistent with GBF's transcriptional-activator function acting on late-gene promoters. Supporting Evidence: PMID:8065317 in vitro-transcribed and -translated GBF binds all three SP60/cotC CAEs in a sequence-specific manner |
| GO:0005829 cytosol | IDA PMID:8125261 Cloning and characterization of the G-box binding factor, an... | KEEP AS NON CORE | Summary: GBF was also detected in the cytosol. As a transcription factor, its functionally relevant site of action is the nucleus; cytosolic detection may reflect a pre-nuclear or non-functional pool. Retained as a non-core localization. Reason: The functional site of GBF is the nucleus, where it binds late-gene promoters. Cytosolic localization is retained as reported but is not the core site of GBF function. Supporting Evidence: PMID:8125261 The predicted protein is highly basic and contains two putative zinc fingers. |
| GO:0006357 regulation of transcription by RNA polymerase II | IMP PMID:8125261 Cloning and characterization of the G-box binding factor, an... | ACCEPT | Summary: GBF regulates transcription of protein-coding late genes, activating the post-aggregative gene program in response to cAMP. This is a core biological process directly tied to its transcription-factor activity. Reason: GBF is required for induction of cell-type-specific late genes and functions as a transcriptional activator, placing it squarely in regulation of RNA polymerase II transcription. This is a core process annotation. Supporting Evidence: PMID:8125261 the loss of late gene induction during development or in response to extracellular cAMP PMID:8125261 GBF acts as an extracellular cAMP-responsive transcriptional activator regulating late gene expression and is an essential component of a developmental switch between aggregation and cellular morphogenesis |
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