id: Q6NVU6 gene_symbol: UFSP1 product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:9606 label: Homo sapiens description: >- UFSP1 (UFM1-specific protease 1) is a cytosolic thiol-dependent (cysteine-type) isopeptidase of the peptidase C78 family and a paralog of UFSP2. The catalytically active human protein is produced from an upstream near-cognate (217CUG) initiation codon, generating an N-terminally extended form that contains the catalytic Cys protease domain; the previously annotated 445AUG-initiated short form lacks the active site and is inactive. UFSP1 carries out two reactions in the UFM1 (ubiquitin-fold modifier 1) conjugation system - it cleaves pro-UFM1 to expose the C-terminal glycine required for activation (UFM1 maturation), and it removes UFM1 from conjugated substrates (deUFMylation). It acts early in the pathway, maturing UFM1 and removing an autoinhibitory UFM1 modification on the E2 enzyme UFC1, and in vitro disassembles polyUFM1 chains. UFSP1 and UFSP2 act redundantly in pro-UFM1 maturation, but differ in substrate specificity and localization (UFSP2, not UFSP1, deUFMylates the ribosomal subunit RPL26). existing_annotations: - term: id: GO:0071567 label: deUFMylase activity evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: enables review: summary: Phylogenetic inference of UFM1-specific protease (deUFMylase) activity across the UFSP family. This is the core molecular function of UFSP1 and is directly supported by experimental evidence for the human protein. action: ACCEPT reason: deUFMylase activity is the central, experimentally confirmed function of UFSP1; the IBA call is corroborated by direct biochemical assays. supported_by: - reference_id: PMID:35525273 supporting_text: both UFSP1 and UFSP2 mediate maturation of UFM1 and de-UFMylation of target proteins - term: id: GO:0005829 label: cytosol evidence_type: IEA original_reference_id: GO_REF:0000044 qualifier: located_in review: summary: Electronic localization to cytosol, consistent with the experimentally determined cytosolic localization of UFSP1. action: ACCEPT reason: Cytosol is the documented site of UFSP1 action; the IEA call agrees with direct subcellular fractionation evidence. supported_by: - reference_id: file:human/UFSP1/UFSP1-uniprot.txt supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm, cytosol' - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32296183 qualifier: enables review: summary: High-throughput binary (Y2H) human interactome screen recording ~40 partners (largely transcription factors and unrelated proteins). The bare protein binding term is uninformative and the partners do not converge on a coherent UFSP1 function. action: KEEP_AS_NON_CORE reason: Records real binary interactions but the generic term carries no functional information and the partners are not part of UFSP1's UFM1-protease function; retained as non-core per curation guidelines on protein binding. supported_by: - reference_id: file:human/UFSP1/UFSP1-goa.tsv supporting_text: GO:0005515 - term: id: GO:0071567 label: deUFMylase activity evidence_type: IEA original_reference_id: GO_REF:0000120 qualifier: enables review: summary: Automated electronic annotation of deUFMylase activity, redundant with and consistent with the experimentally supported IDA annotations. action: ACCEPT reason: Correct core molecular function; agrees with stronger experimental evidence. supported_by: - reference_id: PMID:35926457 supporting_text: UFSP1 effectively cleaved UFM1 from these different substrates - term: id: GO:0071569 label: protein ufmylation evidence_type: IDA original_reference_id: PMID:35525273 qualifier: involved_in review: summary: UFSP1 is involved in protein UFMylation by maturing pro-UFM1, a prerequisite for conjugation, and by reversing UFM1 conjugation. This is the correct biological-process context for its protease activity. action: ACCEPT reason: By generating mature UFM1 and removing an autoinhibitory UFM1 mark on UFC1, UFSP1 directly controls the activation of the UFMylation pathway. supported_by: - reference_id: PMID:35525273 supporting_text: both UFSP1 and UFSP2 mediate maturation of UFM1 and de-UFMylation of target proteins - term: id: GO:0071569 label: protein ufmylation evidence_type: IDA original_reference_id: PMID:35926457 qualifier: involved_in review: summary: Independent demonstration that UFSP1 acts in the UFMylation pathway, controlling its activation by maturing UFM1 and cleaving an autoinhibitory modification on the E2 UFC1. action: ACCEPT reason: Direct evidence that UFSP1 regulates the UFMylation process; correct BP annotation. supported_by: - reference_id: PMID:35926457 supporting_text: UFSP1 acts earlier in the pathway to mature UFM1 and cleave a potential autoinhibitory modification on UFC1, thereby controlling activation of UFMylation - term: id: GO:0005829 label: cytosol evidence_type: IDA original_reference_id: PMID:35926457 qualifier: is_active_in review: summary: Direct subcellular fractionation evidence that endogenous UFSP1 is cytosolic, the compartment in which it acts on UFM1/UFC1. action: ACCEPT reason: IDA-supported active-site localization; distinguishes UFSP1 (cytosolic) from the ER-associated UFSP2-mediated RPL26 deUFMylation. supported_by: - reference_id: PMID:35926457 supporting_text: localization-dependent functions for the two proteases in regulating UFMylation - term: id: GO:0008234 label: cysteine-type peptidase activity evidence_type: IDA original_reference_id: PMID:35525273 qualifier: enables review: summary: UFSP1 is a cysteine (thiol) protease; the active form contains a catalytic Cys protease domain and the Cys-to-Ala mutation abolishes activity. This is the catalytic basis of its UFM1-specific protease activity. action: ACCEPT reason: Direct biochemical and mutagenesis evidence establishes UFSP1 as a cysteine-type peptidase; this is the molecular mechanism underlying its deUFMylase activity. supported_by: - reference_id: PMID:35525273 supporting_text: revealing the presence of a catalytic protease domain containing a Cys active - reference_id: file:human/UFSP1/UFSP1-uniprot.txt supporting_text: 'C->A: Abolished isopeptidase activity' - term: id: GO:0008234 label: cysteine-type peptidase activity evidence_type: IDA original_reference_id: PMID:35926457 qualifier: enables review: summary: Independent confirmation that UFSP1 is an active cysteine-type protease cleaving UFM1 from substrates. action: ACCEPT reason: Corroborates the cysteine-protease mechanism; core molecular function. supported_by: - reference_id: PMID:35926457 supporting_text: UFSP1 effectively cleaved UFM1 from these different substrates - term: id: GO:0051604 label: protein maturation evidence_type: IDA original_reference_id: PMID:35525273 qualifier: involved_in review: summary: UFSP1 mediates maturation of the UFM1 precursor (cleaving pro-UFM1 to expose the C-terminal Gly). Protein maturation is a correct, more general BP capturing this processing role. action: ACCEPT reason: Pro-UFM1 maturation is a directly demonstrated UFSP1 activity and a prerequisite for UFMylation. supported_by: - reference_id: PMID:35525273 supporting_text: both UFSP1 and UFSP2 mediate maturation of UFM1 and de-UFMylation of target proteins - term: id: GO:0051604 label: protein maturation evidence_type: IDA original_reference_id: PMID:35926457 qualifier: involved_in review: summary: Independent evidence that UFSP1 matures UFM1 (proteolytic processing of pro-UFM1 to expose the C-terminal glycine). action: ACCEPT reason: Correct BP annotation for the UFM1-maturation step performed by UFSP1. supported_by: - reference_id: PMID:35926457 supporting_text: An essential first step in the post-translational modification of proteins with UFM1, UFMylation, is the proteolytic cleavage of pro-UFM1 to expose a C-terminal glycine - term: id: GO:0071567 label: deUFMylase activity evidence_type: IDA original_reference_id: PMID:35525273 qualifier: enables review: summary: Direct demonstration that UFSP1 de-UFMylates target proteins, i.e. removes UFM1 conjugated to substrates. Core molecular function. action: ACCEPT reason: deUFMylation of target proteins is directly shown; this is the defining UFSP1 activity. supported_by: - reference_id: PMID:35525273 supporting_text: both UFSP1 and UFSP2 mediate maturation of UFM1 and de-UFMylation of target proteins - term: id: GO:0071567 label: deUFMylase activity evidence_type: IDA original_reference_id: PMID:35926457 qualifier: enables review: summary: UFSP1 cleaves UFM1 from diverse substrates and disassembles polyUFM1 chains in vitro, confirming deUFMylase activity. action: ACCEPT reason: Direct biochemical evidence for deUFMylase activity; core molecular function. supported_by: - reference_id: PMID:35926457 supporting_text: UFSP1 effectively cleaved UFM1 from these different substrates references: - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000044 title: Gene Ontology annotation through association of InterPro records with GO terms findings: [] - id: GO_REF:0000120 title: Combined Automated Annotation using Multiple IEA Methods findings: [] - id: PMID:32296183 title: A reference map of the human binary protein interactome. findings: [] reference_review: relevance: LOW correctness: VERIFIED review_notes: High-throughput binary interactome map (HuRI); records ~40 UFSP1 interactors but none informs the UFM1-protease function. - id: PMID:35525273 title: Human UFSP1 translated from an upstream near-cognate initiation codon functions as an active UFM1-specific protease. findings: - statement: Human UFSP1 is translated from an upstream near-cognate 217CUG codon (eIF2A-mediated), yielding a form that contains a catalytic protease domain with a Cys active site; the canonical 445AUG form lacks the active site. reference_section_type: ABSTRACT - statement: Both UFSP1 and UFSP2 mediate maturation of the UFM1 precursor and de-UFMylation of target proteins; mutation of the catalytic cysteine abolishes activity. reference_section_type: RESULTS reference_review: relevance: HIGH correctness: VERIFIED review_notes: PubMed-verified; establishes human UFSP1 as an active UFM1-specific cysteine protease. - id: PMID:35926457 title: Human UFSP1 is an active protease that regulates UFM1 maturation and UFMylation. findings: - statement: UFSP1 (from a non-canonical start site) is an active protease; cells lacking both UFSPs show complete loss of UFMylation from absence of mature UFM1. reference_section_type: ABSTRACT - statement: UFSP1 acts early to mature UFM1 and cleave a potential autoinhibitory UFM1 modification on UFC1; unlike UFSP2 it does not remove UFM1 from RPL26. UFSP1 is cytosolic and disassembles polyUFM1 chains in vitro. reference_section_type: RESULTS reference_review: relevance: HIGH correctness: VERIFIED review_notes: PubMed-verified; defines distinct substrate specificity and cytosolic localization of UFSP1 vs UFSP2. core_functions: - description: UFM1-specific cysteine (thiol) protease that matures pro-UFM1 by cleaving its C-terminus to expose the activating C-terminal glycine, and removes UFM1 from conjugated substrates (deUFMylation), thereby controlling activation and reversal of UFMylation. molecular_function: id: GO:0071567 label: deUFMylase activity locations: - id: GO:0005829 label: cytosol supported_by: - reference_id: PMID:35525273 supporting_text: both UFSP1 and UFSP2 mediate maturation of UFM1 and de-UFMylation of target proteins - reference_id: PMID:35926457 supporting_text: UFSP1 effectively cleaved UFM1 from these different substrates - description: Cysteine-type peptidase activity (catalytic Cys protease domain) underlying UFSP1's UFM1-specific protease function; the active form arises from a non-canonical upstream start codon. molecular_function: id: GO:0008234 label: cysteine-type peptidase activity locations: - id: GO:0005829 label: cytosol supported_by: - reference_id: PMID:35525273 supporting_text: revealing the presence of a catalytic protease domain containing a Cys active - reference_id: file:human/UFSP1/UFSP1-uniprot.txt supporting_text: 'C->A: Abolished isopeptidase activity' proposed_new_terms: [] suggested_questions: - question: What is the full physiological substrate repertoire of UFSP1 deUFMylation beyond UFC1, and how does it partition with UFSP2 in vivo? - question: How is the non-canonical 217CUG translation of the active UFSP1 isoform regulated, and does its abundance limit UFMylation flux under stress? suggested_experiments: - description: UFM1-conjugate proteomics in UFSP1-knockout, UFSP2-knockout and double-knockout cells to define non-redundant versus shared deUFMylation substrates. - description: Ribosome profiling / reporter assays to quantify eIF2A-dependent initiation at the 217CUG codon and test how it controls the amount of catalytically active UFSP1.