C8orf17 (MOST-1, MOLT-4 sequence tag-1) is a putative 99-amino-acid, basic, hydrophilic protein encoded by an intronless open reading frame at 8q24.3 lying within an intron of TRAPPC9. It has no recognisable domain or sequence motif, no transmembrane segment, and no annotated orthologue outside human; HGNC classifies the locus type as unknown and Ensembl annotates its transcript as TEC (to be experimentally confirmed). The transcript is of low abundance and was reported in a subset of normal tissues and in all cancer cell lines tested, with higher levels or copy number in high-grade breast and prostate carcinomas. One study, using an antibody raised to a synthetic peptide, reported cytoplasmic staining, co-immunoprecipitation with ferritin light chain, TSPO and immunoglobulin mu/delta heavy chains, and reduced proliferation with increased apoptosis after knockdown in DU145 prostate cancer cells. No molecular activity is known.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:17143515 Cellular expression, localization and interactions of the pr... | REMOVE | Summary: Bare protein binding from yeast two-hybrid plus co-immunoprecipitation with ferritin light chain (FTL). Reason: Generic protein binding is uninformative and is removed under project policy; removal does not dispute the reported FTL interaction. The interaction suggests no specific molecular activity (no ferritin-related function has been tested), so no more informative MF term can be substituted. Supporting Evidence: PMID:17143515 Co-immunoprecipitation assays validated the interactions of MOST-1 with the latter three proteins |
| GO:0005515 protein binding | IPI PMID:17143515 Cellular expression, localization and interactions of the pr... | REMOVE | Summary: Bare protein binding from yeast two-hybrid plus co-immunoprecipitation with the peripheral benzodiazepine receptor (TSPO). Reason: Generic protein binding is uninformative and is removed under project policy; the TSPO interaction is not disputed, but no activity toward TSPO (e.g. ligand or transport effects) has been examined, so no informative MF replacement is supported. Supporting Evidence: PMID:17143515 Co-immunoprecipitation assays validated the interactions of MOST-1 with the latter three proteins |
| GO:0005634 nucleus | IDA PMID:17143515 Cellular expression, localization and interactions of the pr... | UNDECIDED | Summary: Nuclear localisation by IDA from the single characterisation paper. Reason: The cached record is abstract-only and the abstract reports only cytoplasmic localisation (with polar distribution during division). The curator may have seen nuclear staining in the full text, which we cannot inspect. Endogenous product detection rests on one antiserum against a synthetic peptide for a TEC transcript with no orthologue, so we neither accept nor remove. Supporting Evidence: PMID:17143515 MOST-1 displayed cytoplasmic localization in four human cell lines |
| GO:0005737 cytoplasm | IDA PMID:17143515 Cellular expression, localization and interactions of the pr... | ACCEPT | Summary: Cytoplasmic immunostaining in four human cell lines. Reason: Directly stated in the abstract. It is the only location supported in the accessible text, though it comes from one antiserum in one study. Supporting Evidence: PMID:17143515 MOST-1 displayed cytoplasmic localization in four human cell lines |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (SL-0086 Cytoplasm), derived from the same study. Reason: Consistent with the IDA row; it duplicates the same evidence. Supporting Evidence: UniProt:Q9NRJ1 SUBCELLULAR LOCATION: Cytoplasm |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | UNDECIDED | Summary: UniProt subcellular-location mapping of 'Endoplasmic reticulum membrane' (and 'Microsome membrane'), attributed by UniProt to PMID:17143515. Reason: The predicted product is a basic hydrophilic 99-aa protein with no transmembrane segment, so integral ER membrane residence is not expected from sequence; a microsomal fraction signal could reflect peripheral association or aggregation (the paper notes SDS-insoluble high molecular mass forms). The abstract does not mention ER or microsomes and the full text is not available to us, so the UniProt curator's reading cannot be checked. Supporting Evidence: PMID:12665628 encoding a putative hydrophilic polypeptide of 99 amino acids UniProt:Q9NRJ1 Endoplasmic reticulum membrane |
| GO:0008284 positive regulation of cell population proliferation | NAS PMID:17143515 Cellular expression, localization and interactions of the pr... | MARK AS OVER ANNOTATED | Summary: NAS from the authors' interpretation of a knockdown in DU145 cells that reduced proliferation. Reason: A single knockdown in one cancer cell line, from one lab and unreplicated in nearly 20 years. The locus is a TEC transcript with no annotated translation or orthologue, so an RNA-level effect cannot be separated from a protein-level one, and no mechanism links the peptide to proliferation control. The authors themselves describe only a 'putative mitogenic role'. Supporting Evidence: PMID:17143515 Knockdown of MOST-1 expression in DU145 cells resulted in reduced cell proliferation but enhanced apoptosis |
| GO:0043066 negative regulation of apoptotic process | NAS PMID:17143515 Cellular expression, localization and interactions of the pr... | MARK AS OVER ANNOTATED | Summary: NAS from the same DU145 knockdown, which enhanced apoptosis. Reason: Same single unreplicated knockdown as the proliferation row. Increased apoptosis after depletion is an indirect phenotype, not evidence that the protein participates in apoptotic regulation, and the protein-versus-RNA question is unresolved. Supporting Evidence: PMID:17143515 Knockdown of MOST-1 expression in DU145 cells resulted in reduced cell proliferation but enhanced apoptosis |
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Download this section (compressed HTML)Q: Is the C8orf17 ORF translated in human cells? Ribosome profiling and targeted mass spectrometry of a unique peptide would settle whether the TEC transcript encodes a stable protein.
Q: Does the DU145 proliferation/apoptosis phenotype survive an ORF-specific test (start-codon mutation or frame-preserving rescue) rather than transcript knockdown?
Experiment: Tag the endogenous ORF (CRISPR knock-in of a C-terminal HiBiT or epitope tag) in DU145 or MOLT-4 cells and look for translation by ribosome profiling; if a product is detected, determine localisation by co-staining with ER and nuclear markers.
Hypothesis: The C8orf17 ORF produces an endogenous protein.
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