CRT10 (YOL063C) encodes a 957-residue, low-abundance (about 125 molecules per cell) protein built from two copies of the fungal-specific CRT10 domain (Pfam PF08728) with a WD40-like region near the N-terminus. Crt10 is an accessory subunit of the budding-yeast Cul8/Rtt101 cullin-RING ubiquitin ligase: it co-purifies with the cullin Rtt101 and the DDB1-like linker Mms1, binds Mms1 directly and reaches Rtt101 only through Mms1, and associates constitutively rather than in response to DNA damage. It is therefore regarded as a putative substrate receptor (DCAF-like adaptor) of the Rtt101-Mms1 ligase, although no ubiquitination substrate has been identified. Genetically, Crt10 is required for nonfunctional rRNA decay (NRD) of mutant 25S rRNA, a ubiquitin-dependent pathway that also requires Rtt101 and Mms1, but unlike the alternative receptor Mms22 it is not needed for DNA-damage tolerance; Crt10 also exists in a second ligase assembly that contains the Paf1 complex. Crt10 was first identified as a repressor of ribonucleotide reductase (RNR) gene expression: crt10 deletion confers hydroxyurea resistance, partially rescues mec1 lethality and raises basal and damage-induced RNR2/RNR3 transcripts, acting genetically in the Dun1-Crt1 pathway by sustaining CRT1 transcript levels. CRT10 expression is induced by DNA damage and hydroxyurea in a DUN1-dependent manner.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003674 molecular_function | ND GO_REF:0000015 | ACCEPT | Summary: No molecular activity of Crt10 has been demonstrated. The published biochemistry shows only that Crt10 is bridged to Rtt101 by Mms1, from which the authors infer a putative substrate-adaptor role; no substrate, ubiquitination assay or binding specificity for Crt10 has been reported. Reason: The literature was searched (Fu and Xiao 2006; Zaidi et al. 2008; Sakata et al. 2015; large-scale interactome data). The substrate-adaptor role remains a hypothesis drawn from analogy to mammalian DCAFs, so a specific MF term such as ubiquitin-like ligase-substrate adaptor activity (GO:1990756) would currently be an over-reach. The ND annotation accurately represents the state of knowledge. Supporting Evidence: PMID:18704118 Mms22 and Crt10 interact with Rtt101 in an Mms1-dependent manner, suggesting that they could function as substrate-specific adaptors for the Rtt101-based ubiquitin ligase PMID:25534857 provided a molecular framework for the substrate diversity of the E3 complex |
| GO:0005515 protein binding | IPI PMID:18704118 Rtt101 and Mms1 in budding yeast form a CUL4(DDB1)-like ubiq... | REMOVE | Summary: Crt10 co-purifies with the cullin Rtt101 (P47050), but the association is indirect: it depends on the linker Mms1 and is lost with Rtt101-deltaN50, which cannot bind Mms1. Crt10 binds Mms1 directly. Reason: Bare protein binding is uninformative and, for the Rtt101 partner specifically, describes a bridged rather than direct interaction. The biologically meaningful content of this experiment, Crt10 being a subunit of the Rtt101-Mms1 cullin-RING ligase, is captured by part_of Cul8-RING ubiquitin ligase complex (GO:0035361), proposed on the cellular_component row. No informative MF term is supported, so MODIFY is not appropriate. Removal does not dispute the reported interaction. Supporting Evidence: PMID:18704118 The interaction between Crt10 and Rtt101 was dependent on Mms1 ( Fig 4A ). By contrast, Crt10 efficiently interacted with Mms1 in the absence of Rtt101 (data not shown), and Crt10 failed to co-precipitate with Rtt101-ΞN50, which is defective for binding to Mms1 ( Fig 4A ). |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | REMOVE | Summary: Proteome-wide affinity enrichment-MS of GFP-tagged yeast strains recovered the Crt10-Rtt101 association, independently confirming the co-complex relationship seen in targeted purifications. Reason: Generic protein binding from a high-throughput co-complex screen carries no functional information and cannot distinguish the direct Crt10-Mms1 contact from the bridged Crt10-Rtt101 association. Complex membership is represented by GO:0035361 instead. Removal does not dispute the reported interaction. Supporting Evidence: PMID:37968396 we develop a sensitive high-throughput method using highly reproducible affinity enrichment coupled to mass spectrometry combined with a quantitative two-dimensional analysis strategy to comprehensively map the interactome of Saccharomyces cerevisiae |
| GO:0005575 cellular_component | ND GO_REF:0000015 | MODIFY | Summary: The subcellular location of Crt10 has not been determined, but its complex membership has: Crt10 co-purifies by TAP-MS with Rtt101 and Mms1 (not with the Cdc53 cullin), associates with them constitutively, and is a component of two distinct Rtt101-Mms1 ligase assemblies, one of which contains the Paf1 complex. Reason: Cellular-component data do exist in the form of complex membership, so the no-data root term should be replaced by part_of Cul8-RING ubiquitin ligase complex (GO:0035361), whose definition names Mms1 as the adaptor and allows several specificity factors. Comparator check: the alternative substrate receptor Mms22, standing in the same role, carries IDA part_of GO:0035361 from SGD, as do Rtt101, Mms1 and Hrt1; Crt10's absence looks like a gap rather than a convention, because the paper that showed Crt10 in the complex (PMID:18704118) was curated only to protein binding. No subcellular localisation (nucleus vs cytoplasm) has been experimentally established, so no location term is proposed. Proposed replacements: Cul8-RING ubiquitin ligase complex Supporting Evidence: PMID:18704118 Crt10, a regulator of RNR gene transcription ( Fu & Xiao, 2006 ), co-purified with both Rtt101 and Mms1, but not with Cdc53 PMID:18704118 Crt10 interacted with Rtt101 in the absence of MMS, whereas the interaction between Mms22 and Rtt101 was stimulated after MMS treatment PMID:25534857 We also identified two distinct Crt10-containing E3 complexes, one of which contained the Paf1 complex file:yeast/CRT10/CRT10-uniprot.txt Component of a cullin-RING ligase (CRL) composed of 4 |
| GO:0070651 nonfunctional rRNA decay | IGI PMID:25534857 Crt10 directs the cullin-E3 ligase Rtt101 to nonfunctional 2... | ACCEPT | Summary: Genetic interaction with MMS1 (SGD:S000006368) places Crt10 in the Rtt101-Mms1-dependent pathway that clears nonfunctional mutant 25S rRNA. Reason: 25S NRD is a ubiquitin-dependent clearance pathway whose E3 is Rtt101-Mms1. Crt10 is an accessory subunit of that ligase that, unlike Mms22, specifies its NRD rather than DNA-repair function, so Crt10 contributes part of the work of the process (as a component of the enzyme that performs it) rather than being a substrate or a distant regulator. This is the best-established biological role of Crt10. The cached record is abstract-only; the abstract explicitly states the requirement and the curators read the full paper. Supporting Evidence: PMID:25534857 We herein demonstrated that another accessory component, Crt10 was required for 25S NRD, but not for DNA repair, suggesting that this accessory component specifies the function of the E3 complex differently. |
| GO:0070651 nonfunctional rRNA decay | IMP PMID:25534857 Crt10 directs the cullin-E3 ligase Rtt101 to nonfunctional 2... | ACCEPT | Summary: crt10 deletion impairs decay of nonfunctional mutant 25S rRNA. Reason: Same claim as the IGI row, from the same study; the deletion phenotype together with Crt10's physical membership in the Rtt101-Mms1 E3 supports direct participation as a ligase subunit. Core function. Supporting Evidence: PMID:25534857 NRD of 25S rRNA required cullin-E3 ligase Rtt101 and its associating factor Mms1 PMID:25534857 We herein demonstrated that another accessory component, Crt10 was required for 25S NRD, but not for DNA repair |
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Download this section (compressed HTML)Q: Does Crt10 act as the substrate receptor that recruits ribosomal proteins of nonfunctional 60S subunits to Rtt101-Mms1 for ubiquitination, and is it sufficient to confer this specificity?
Q: Is the RNR-repression phenotype of crt10 deletion (via reduced CRT1 transcript) mediated by the Rtt101-Mms1-Crt10 ligase, and if so, which substrate links it to CRT1 transcription? Until this is known, a transcription-regulation process term for Crt10 would rest on indirect genetic evidence only.
Q: Where in the cell is Crt10 active? No localisation has been reported, so neither a nuclear nor a cytoplasmic location can currently be asserted.
Experiment: Quantitative ubiquitin-remnant proteomics comparing wild-type, crt10, mms22 and rtt101 strains expressing an NRD-inducing 25S rRNA mutant, to identify Crt10-dependent ubiquitination sites on 60S ribosomal proteins.
Type: proteomics
Experiment: In vitro reconstitution of Rtt101-Mms1-Hrt1 with or without Crt10, testing ubiquitination of purified nonfunctional 60S subunits, and crosslinking to establish direct Crt10-substrate contact.
Type: biochemistry
Experiment: Endogenous GFP-tagged Crt10 imaging (low abundance, so with sensitive detection) under normal growth, HU and MMS treatment to establish its subcellular location.
Type: cell biology
Protein required for the degradation of mutant 25S rRNAs; functions in Mms1 pathway of nonfunctional 25S rRNA decay; expression induced by DNA damage and null mutations confer increased resistance to hydroxyurea; N-terminal region has a leucine repeat and a WD40 repeat
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