JEM1/KAR8 encodes an ER membrane DnaJ/Hsp40-family co-chaperone with a lumen-facing J-domain. Jem1 works with the ER Hsp70 Kar2/BiP and overlaps partly with Scj1 to support ER protein folding and ERAD of soluble luminal misfolded substrates by keeping them soluble and retrotranslocation competent. Jem1 is also required for nuclear membrane fusion during mating karyogamy at the ER/nuclear envelope membrane system.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0051087 protein-folding chaperone binding | IBA GO_REF:0000033 | ACCEPT | Summary: IBA is consistent with Jem1 as an ER J-domain co-chaperone for Kar2/BiP. Reason: J-domain co-chaperone function is the best-supported molecular role. Supporting Evidence: PMID:9148890 JEM1p likely assists the functions of BiP, Hsp70 in the ER, including karyogamy. file:yeast/JEM1/JEM1-deep-research-falcon.md Jem1p is an ER J-domain co-chaperone working within the Kar2/BiP chaperone system. |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference agrees with direct ER membrane localization. Reason: The ER is the compartment for Jem1's folding, ERAD, and karyogamy functions. Supporting Evidence: PMID:9148890 protein was anchored in the endoplasmic reticulum (ER) membrane and its J-domain |
| GO:0034975 protein folding in endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: This matches Jem1/Scj1/Kar2 roles in ER folding and quality control. Reason: Jem1 supports ER folding and ERAD substrate handling. Supporting Evidence: PMID:11381090 Jem1p and Scj1p function as major partners for BiP in the ERAD process. PMID:9817751 Jem1p and Scj1p appear to have partially overlapping functions as cofactors for Kar2p. |
| GO:0051787 misfolded protein binding | IBA GO_REF:0000033 | ACCEPT | Summary: Misfolded protein binding fits the ERAD substrate-solubility evidence. Reason: This term is more informative than generic unfolded protein binding for the ERAD role. Supporting Evidence: PMID:11381090 aberrant immature proteins aggregated and migrated in the densest fraction |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular mapping is consistent with direct ER membrane evidence. Reason: Jem1 is a single-pass ER membrane protein with a lumen-facing J-domain. Supporting Evidence: PMID:9148890 protein was anchored in the endoplasmic reticulum (ER) membrane and its J-domain |
| GO:0031965 nuclear membrane | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: Nuclear membrane localization is plausible but broad. Reason: Keep as valid context for karyogamy, but the ER membrane/nuclear outer membrane network terms are more precise. Supporting Evidence: PMID:15282802 localization data for 21 other proteins |
| GO:0005515 protein binding | IPI PMID:12493774 Nep98p is a component of the yeast spindle pole body and ess... | MARK AS OVER ANNOTATED | Summary: The MPS3/Nep98 interaction is relevant but GO:0005515 is uninformative. Reason: Protein binding hides the more specific J-domain co-chaperone and karyogamy biology. Supporting Evidence: PMID:12493774 screened for partner proteins for Jem1p by the yeast two-hybrid...identified Nep98p |
| GO:0036503 ERAD pathway | IMP PMID:11381090 Molecular chaperones in the yeast endoplasmic reticulum main... | ACCEPT | Summary: Direct ERAD assays support this process annotation. Reason: Jem1 helps keep soluble luminal ERAD substrates retrotranslocation competent. Supporting Evidence: PMID:11381090 one role for the lumenal Hsp70 chaperone system in the export of aberrant proteins |
| GO:0051082 unfolded protein binding | IMP PMID:9148890 The yeast JEM1p is a DnaJ-like protein of the endoplasmic re... | MODIFY | Summary: Unfolded protein binding is too broad for the evidence. Reason: Misfolded protein binding better captures Jem1's ERAD substrate-handling role. Proposed replacements: misfolded protein binding Supporting Evidence: PMID:11381090 BiP-Jem1p-Scj1p chaperone system is to retain ERAD substrates as lower molecular weight species. |
| GO:0051087 protein-folding chaperone binding | IGI PMID:9148890 The yeast JEM1p is a DnaJ-like protein of the endoplasmic re... | ACCEPT | Summary: Genetic evidence supports chaperone binding as the J-domain co-chaperone function. Reason: Jem1 works with Kar2/BiP during ER and nuclear fusion processes. Supporting Evidence: PMID:9148890 DnaJ-like proteins are functional partners for Hsp70 molecular chaperones. |
| GO:0005783 endoplasmic reticulum | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | ACCEPT | Summary: High-throughput ER localization is consistent with direct evidence. Reason: ER localization is core to Jem1 function. Supporting Evidence: PMID:9148890 protein was anchored in the endoplasmic reticulum (ER) membrane |
| GO:0000742 karyogamy involved in conjugation with cellular fusion | IMP PMID:10069807 Genetic interactions between KAR7/SEC71, KAR8/JEM1, KAR5, an... | ACCEPT | Summary: Jem1/Kar8 has a defining role in nuclear fusion during mating. Reason: Karyogamy is a directly characterized JEM1 process, not a generic downstream phenotype. Supporting Evidence: PMID:10069807 Overexpression of KAR8/JEM1 (but not SEC63) strongly suppressed the mating...defect of kar2-1 |
| GO:0005783 endoplasmic reticulum | IDA PMID:9148890 The yeast JEM1p is a DnaJ-like protein of the endoplasmic re... | ACCEPT | Summary: Direct experimental localization supports ER annotation. Reason: The ER is the core cellular compartment for Jem1. Supporting Evidence: PMID:9148890 protein was anchored in the endoplasmic reticulum (ER) membrane |
| GO:0034975 protein folding in endoplasmic reticulum | IGI PMID:9817751 A role for the DnaJ homologue Scj1p in protein folding in th... | ACCEPT | Summary: Genetic evidence supports overlapping Jem1/Scj1 ER folding functions. Reason: Jem1 and Scj1 are functionally overlapping ER DnaJ proteins. Supporting Evidence: PMID:9817751 Jem1p and Scj1p appear to have partially overlapping functions as cofactors for Kar2p. |
| GO:0042175 nuclear outer membrane-endoplasmic reticulum membrane network | IDA PMID:15282802 Localization of proteins that are coordinately expressed wit... | UNDECIDED | Summary: The ER/nuclear-envelope localization fits Jem1 biology, but the PMID:15282802 IDA claim cannot be independently verified from the accessible abstract. Reason: PMID:15282802 is a GFP localization survey whose accessible abstract does not name Jem1/KAR8, and the full text is unavailable here. PMID:9148890 supports ER membrane anchoring as biological context, but it does not directly verify this specific PMID:15282802 IDA localization record. Supporting Evidence: PMID:15282802 localization data for 21 other proteins PMID:9148890 protein was anchored in the endoplasmic reticulum (ER) membrane and its J-domain |
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