BICC1 (BicC family RNA-binding protein 1) encodes an evolutionarily conserved RNA-binding protein that functions as a post-transcriptional regulator of gene expression. The protein contains three N-terminal KH (K Homology) domains that mediate RNA binding, and a C-terminal SAM (sterile alpha motif) domain that enables self-polymerization and protein-protein interactions. BICC1 acts primarily as a translational repressor, binding specific mRNA 3'UTRs and recruiting the CCR4-NOT deadenylase complex or microRNA machinery to silence target transcripts. Key functions include negative regulation of the canonical Wnt signaling pathway and modulation of cAMP signaling through regulation of target mRNAs such as PKD2, ADCY6, and DVL2. BICC1 localizes to cytoplasmic P-bodies where it forms oligomeric silencing platforms. Loss of BICC1 function causes polycystic kidney disease in mice and humans, and mutations are associated with cystic renal dysplasia. BICC1 is also involved in left-right axis determination during embryonic development.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: BICC1 is well-established as a cytoplasmic protein. Studies show that endogenous BICC1 concentrates in discrete cytoplasmic foci that co-localize with P-body markers (GW182, HEDLS). The SAM domain drives self-polymerization leading to formation of cytoplasmic puncta (Rothe et al. 2015, PMC4561730). Reason: Strongly supported by multiple studies demonstrating BICC1 localizes to cytoplasmic P-bodies where it forms silencing platforms for mRNA regulation. UniProt also indicates cytoplasmic localization by similarity. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md BICC1 carries out its function in the cytoplasm, where it associates with macromolecular RNA-protein granules. Endogenous BICC1 protein concentrates in discrete cytoplasmic foci that co-localize with P-body markers (e.g. GW182 and HEDLS). |
| GO:0003676 nucleic acid binding | IEA GO_REF:0000002 | MODIFY | Summary: This annotation is too general. BICC1 specifically binds RNA, not DNA. The protein contains three KH domains that are classic RNA-binding motifs, and studies have identified specific RNA targets including a 32-nucleotide stem-loop structure in target mRNA 3'UTRs (Zhang et al. 2014, PMC3953263). Reason: While technically not wrong (RNA is a nucleic acid), this term is overly broad and does not capture the specific RNA-binding function of BICC1. The more specific term GO:0003723 (RNA binding) should be used. Proposed replacements: RNA binding Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md BICC1's three KH domains enable it to bind RNA with sequence/structure specificity. Canonical KH domains recognize short nucleotide motifs, often polypyrimidine tracts, but in BICC1 the recognition appears to involve RNA secondary structure. |
| GO:0003723 RNA binding | IEA GO_REF:0000120 | ACCEPT | Summary: BICC1 is definitively an RNA-binding protein. It contains three KH domains that mediate RNA binding. Multiple studies have demonstrated direct RNA binding including identification of a 32-nt stem-loop binding element in the Cripto-1 3'UTR (Zhang et al. 2014). RIP-seq in Xenopus identified 63 direct mRNA targets. Reason: Core molecular function supported by extensive experimental evidence including biochemical studies (EMSA, RNase footprinting) and proteomics (interactome capture). The KH domains are well-characterized RNA-binding motifs. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md Biochemical analyses (EMSA and footprinting) confirm that BICC1's N-terminal half (containing the KH/KHL domains) directly binds RNA hairpins - for instance, BICC1 protects the Cripto-1 3'UTR stem-loop from RNase cleavage, highlighting a direct RNA-protein interaction. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Duplicate annotation of cytoplasmic localization. This IEA annotation based on UniProt subcellular location is consistent with the IBA annotation and experimental evidence showing BICC1 in cytoplasmic P-bodies. Reason: Cytoplasmic localization is well-supported. While this duplicates the IBA annotation, both are accurate. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md BICC1 carries out its function in the cytoplasm, where it associates with macromolecular RNA-protein granules. |
| GO:0006402 mRNA catabolic process | IEA GO_REF:0000107 | ACCEPT | Summary: BICC1 participates in mRNA catabolism through recruitment of the CCR4-NOT deadenylase complex. In Drosophila, Bic-C physically associates with CCR4-NOT to deadenylate bound transcripts. This promotes mRNA poly(A) tail shortening which can lead to mRNA degradation (Rothe et al. 2015, PMC4561730). Reason: BICC1 recruits mRNA decay machinery to target transcripts. The CCR4-NOT deadenylase association is established and deadenylation is a key step in mRNA catabolism. However, note that BICC1's primary role may be translational repression rather than degradation per se. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md Drosophila Bic-C physically associates with the CCR4-NOT deadenylase complex to deadenylate bound transcripts (including its own mRNA), indicating that BICC1 can induce mRNA poly(A) tail shortening to inhibit translation. |
| GO:0006402 mRNA catabolic process | ISS GO_REF:0000024 | ACCEPT | Summary: Duplicate annotation of mRNA catabolic process. The ISS annotation from ortholog transfer is consistent with the IEA annotation and mechanistic evidence of CCR4-NOT deadenylase recruitment. Reason: Supported by evidence of BICC1 recruiting deadenylase machinery, though primary role is likely translational silencing with catabolism as a secondary outcome. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md BICC1 can recruit mRNA decay and translational inhibition machinery. |
| GO:0007368 determination of left/right symmetry | ISS GO_REF:0000024 | ACCEPT | Summary: BICC1 is involved in left-right axis determination during embryonic development. Mouse Bicc1 knockout mutants exhibit visceral organs with random laterality due to disrupted embryonic node signaling. BICC1 binds and regulates Dand5 mRNA, an inhibitor of Nodal signaling crucial for left-right asymmetry (Rothe et al. 2015, PMC4561730; Dowdle et al. 2022). Reason: Well-supported by mouse knockout studies showing left-right patterning defects and identification of Dand5 as a BICC1 target mRNA critical for establishing asymmetry at the embryonic node. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md Mouse Bicc1 knockout or spontaneous mutants (such as jcpk and bpk alleles) exhibit left-right patterning defects - the visceral organs show random laterality due to disrupted embryonic node signaling. This is attributed to misregulation of molecular cues at the embryonic node, where BICC1 is needed for planar cell polarity and proper orientation of motile cilia. Indeed, Bicc1 was recently shown to bind and regulate the mRNA of Dand5 (an inhibitor of Nodal signaling crucial for left-right asymmetry), linking BICC1 to left-right axis specification. |
| GO:0003723 RNA binding | HDA PMID:22658674 Insights into RNA biology from an atlas of mammalian mRNA-bi... | ACCEPT | Summary: BICC1 was identified as an mRNA-binding protein in the mRNA interactome capture study by Castello et al. 2012. This high-throughput UV crosslinking approach identified BICC1 among 860 proteins that qualify as RBPs by biochemical and statistical criteria in HeLa cells. Reason: The interactome capture methodology provides robust biochemical evidence for RNA binding. This complements the detailed mechanistic studies showing KH domain-mediated RNA binding. Supporting Evidence: PMID:22658674 We identify 860 proteins that qualify as RBPs by biochemical and statistical criteria, adding more than 300 RBPs to those previously known and shedding light on RBPs in disease, RNA-binding enzymes of intermediary metabolism, RNA-binding kinases, and RNA-binding architectures. |
| GO:0090090 negative regulation of canonical Wnt signaling pathway | IDA PMID:21922595 Two mutations in human BICC1 resulting in Wnt pathway hypera... | ACCEPT | Summary: BICC1 acts as a negative regulator of canonical Wnt signaling. Kraus et al. 2012 demonstrated that human BICC1 blocks canonical Wnt signaling, similar to its mouse counterpart. Two patient mutations were characterized - a nonsense mutation in the KH domain caused complete loss of Wnt inhibitory activity, while a SAM domain mutation reduced activity by 22%. BICC1 inhibits Dishevelled-2 (DVL2), a central Wnt signal transducer (Rothe et al. 2015, PMC4561730). Reason: Core function supported by direct experimental evidence in the cited paper. The mechanistic basis involves regulation of Dvl2 and potentially other Wnt pathway components. Loss of BICC1 causes ectopic Wnt/beta-catenin activity during development. Supporting Evidence: PMID:21922595 In mice, Bicc1 blocks canonical Wnt signaling, mostly via its SAM domain. We show that the human BICC1, similar to its mouse counterpart, blocks canonical Wnt signaling. The nonsense mutation identified results in a complete loss of Wnt inhibitory activity. The point mutation in the SAM domain has a similar effect to a complete SAM domain deletion, resulting in a 22% loss of activity. file:human/BICC1/BICC1-deep-research-openai.md A study by Rothe et al. (2015) showed that BICC1 normally inhibits Dishevelled-2 (DVL2), a central Wnt signal transducer: BICC1 binds the Dvl2 mRNA or interacts with DVL2 protein complexes, and when BICC1 polymerization is disrupted, DVL2 levels and Wnt activity rise abnormally. |
| GO:0000956 nuclear-transcribed mRNA catabolic process | IBA GO_REF:0000033 | NEW | Summary: Proposed new annotation based on BICC1's role in mRNA regulation. BICC1 recruits the CCR4-NOT deadenylase complex to target mRNAs, promoting their deadenylation and subsequent degradation. This specifically applies to nuclear-transcribed mRNAs. Reason: While GO:0006402 (mRNA catabolic process) is already annotated, the more specific term for nuclear-transcribed mRNA catabolism may be appropriate given BICC1's targets are conventional mRNAs. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md Drosophila Bic-C physically associates with the CCR4-NOT deadenylase complex to deadenylate bound transcripts. |
| GO:0017148 negative regulation of translation | IBA GO_REF:0000033 | NEW | Summary: BICC1 functions as a translational repressor. It binds target mRNA 3'UTRs and typically represses their translation through multiple mechanisms including deadenylation and recruitment of microRNA machinery. Validated targets include Cripto-1, Pkd2, and Wnt11b mRNAs (Zhang et al. 2014, PMC3953263; Dowdle et al. 2022). Reason: This represents a core molecular function of BICC1 that is well-documented but not currently annotated. BICC1 acts as a translational repressor by binding 3'UTRs and forming silencing complexes. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md BICC1 primarily acts as a post-transcriptional regulator of gene expression. It recognizes specific RNA sequences/structures in the 3' untranslated regions (3'UTRs) of target mRNAs and typically represses their translation or reduces their stability. |
| GO:0036464 cytoplasmic ribonucleoprotein granule | IDA GO_REF:0000033 | NEW | Summary: BICC1 localizes to cytoplasmic P-bodies, which are ribonucleoprotein granules involved in mRNA storage, decay, and microRNA-mediated silencing. The SAM domain drives oligomerization and formation of these cytoplasmic puncta (Rothe et al. 2015, PMC4561730). Reason: More specific cellular component than general cytoplasm. BICC1 specifically concentrates in P-bodies where it forms silencing platforms. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md Endogenous BICC1 protein concentrates in discrete cytoplasmic foci that co-localize with P-body markers (e.g. GW182 and HEDLS). P-bodies are sites of mRNA storage, decay, and microRNA-mediated silencing, suggesting BICC1 functions within these structures to tether and regulate target mRNAs. |
| GO:0000932 P-body | NAS | NEW | Summary: Added to align core_functions with existing annotations. Reason: Core function term not present in existing_annotations. Supporting Evidence: file:human/BICC1/BICC1-deep-research-openai.md Endogenous BICC1 protein concentrates in discrete cytoplasmic foci that co-localize with P-body markers (e.g. GW182 and HEDLS). P-bodies are sites of mRNA storage, decay, and microRNA-mediated silencing. |
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