POP2 (also called CAF1) encodes a CCR4-associated deadenylase subunit of the CCR4-NOT complex. Pop2p has intrinsic poly(A)-preferring 3'-5' RNase D/DEDD-family ribonuclease activity (S44/E46 active site; also degrades poly(U)/poly(C) but not oligo(G)) and works with Ccr4p to shorten mRNA poly(A) tails, promoting deadenylation-dependent mRNA decay. Beyond its own catalytic activity, Pop2/Caf1 has a key architectural/scaffold role: Not1's MIF4G-like domain binds Caf1, which in turn binds the Ccr4 LRR domain to tether the Ccr4 nuclease into the complex; in budding yeast Ccr4 is the primary in vivo catalytic deadenylase and Pop2 catalytic activity is dispensable for several phenotypes. The complex is largely cytoplasmic, relocalizes to P-bodies under stress, and also contributes to transcription elongation regulation (6AU/MPA sensitivity), rDNA stability via repression of E-pro antisense transcripts, and post-transcriptional control of autophagy (ATG mRNA deadenylation).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000288 nuclear-transcribed mRNA catabolic process, deadenylation-dependent decay | IBA GO_REF:0000033 | ACCEPT | Summary: CAF1/Pop2p functions in deadenylation-dependent mRNA decay as part of the CCR4-NOT deadenylase. A classic reporter pulse-chase showed that in caf1Ξ cells the MFA2pG poly(A) tail shortens at only ~2-3 nt/min versus ~13 nt/min in wild type, with ~2-3-fold reporter stabilization, demonstrating that Caf1/Pop2 is required for normal in vivo deadenylation kinetics upstream of decay. Reason: Pop2p is required for efficient mRNA deadenylation and degradation in vivo, consistent with a role in deadenylation-dependent decay. Supporting Evidence: PMID:11410650 supports the involvement of Pop2p in mRNA deadenylation in vivo file:yeast/POP2/POP2-deep-research-falcon.md MFA2pG poly(A) tail shortens at ~13 nt/min file:yeast/POP2/POP2-deep-research-falcon.md in **ccr4Ξ and caf1Ξ** strains deadenylation proceeds at only **~2β3 nt/min** file:yeast/POP2/POP2-deep-research-perplexity.md See deep research file for comprehensive analysis |
| GO:0004535 poly(A)-specific ribonuclease activity | IBA GO_REF:0000033 | ACCEPT | Summary: Pop2p has intrinsic poly(A)-specific ribonuclease activity as a deadenylase subunit. The X-ray structure of the Pop2 RNase D domain confirmed in vitro RNase activity with a preference for poly(A); however purified Pop2 also degrades poly(U) and poly(C) (but not oligo(G)), so the poly(A) preference is subtle rather than strict. Reason: Recombinant Pop2p catalytic domain degrades poly(A), supporting poly(A)-specific ribonuclease activity; structural and biochemical work assigns this activity to the RNase D domain. Supporting Evidence: PMID:11410650 A recombinant Pop2p fragment encompassing the putative catalytic domain degrades poly(A) in vitro demonstrating that Pop2p is a nuclease file:yeast/POP2/POP2-deep-research-falcon.md purified Pop2 displays **in vitro RNase activity** file:yeast/POP2/POP2-deep-research-falcon.md Substrate testing showed activity toward **poly(A)** and also **poly(U)** and **poly(C)**, but **not oligo(G)**, with competition assays indicating a **subtle preference for poly(A)** |
| GO:0000932 P-body | IBA GO_REF:0000033 | ACCEPT | Summary: Pop2p localizes to P-bodies, consistent with its role in mRNA decay pathways. Reason: Reduced P-body accumulation of Pop2p is observed when Q/N-rich regions are deleted, supporting P-body localization. Supporting Evidence: PMID:18611963 reduced P-body accumulation of Ccr4p, Pop2p and Dhh1p after deletion of these domains |
| GO:0030015 CCR4-NOT core complex | IBA GO_REF:0000033 | ACCEPT | Summary: CAF1/Pop2p is a core subunit of the CCR4-NOT complex. Structural work on the yeast nuclease module shows Not1 acts as the scaffold, its MIF4G-like domain binds Caf1, and Caf1 in turn binds the Ccr4 LRR domain, thereby tethering the Ccr4 nuclease into the complex - an architectural role that explains why pop2Ξ also strips Ccr4 from the complex. Reason: Complex purification and interaction data place CAF1/Pop2p within the CCR4-NOT core module, where it bridges Not1 and Ccr4. Supporting Evidence: PMID:11733989 The 1.0 MDa complex was found to contain CCR4, CAF1, NOT1-5 and two new proteins, CAF40 and CAF130 file:yeast/POP2/POP2-deep-research-falcon.md its central **MIF4G-like domain binds Caf1**, and **Caf1 binds the LRR domain of Ccr4**, thereby **tethering the Ccr4 nuclease domain** file:yeast/POP2/POP2-deep-research-falcon.md pop2Ξ causes the complex to lose both Pop2 and Ccr4 |
| GO:0003676 nucleic acid binding | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: Nucleic acid binding is overly broad for CAF1/Pop2p and adds little beyond specific RNA/deadenylase terms. Reason: More specific RNA binding and poly(A)-specific ribonuclease activities capture the functional role. Supporting Evidence: GO_REF:0000002 InterPro domain mapping |
| GO:0003723 RNA binding | IEA GO_REF:0000043 | ACCEPT | Summary: RNA binding is consistent with CAF1/Pop2p deadenylase function. Reason: Pop2p targets mRNA poly(A) tails as part of the deadenylase complex, consistent with RNA binding. Supporting Evidence: GO_REF:0000043 UniProt keyword mapping |
| GO:0004518 nuclease activity | IEA GO_REF:0000043 | MODIFY | Summary: General nuclease activity is too broad; CAF1/Pop2p is specifically a poly(A)-directed 3'-5' exonuclease. Reason: Pop2p specifically degrades poly(A) tails and is annotated more precisely as a poly(A)-specific ribonuclease. Proposed replacements: poly(A)-specific ribonuclease activity Supporting Evidence: GO_REF:0000043 UniProt keyword mapping |
| GO:0004527 exonuclease activity | IEA GO_REF:0000043 | MODIFY | Summary: Broad exonuclease activity should be replaced by the specific 3'-5' RNA exonuclease activity of Pop2p. Reason: Pop2p degrades poly(A) tails via 3'-5' exonucleolytic activity. Proposed replacements: 3'-5'-RNA exonuclease activity Supporting Evidence: GO_REF:0000043 UniProt keyword mapping |
| GO:0004535 poly(A)-specific ribonuclease activity | IEA GO_REF:0000120 | ACCEPT | Summary: Pop2p has intrinsic poly(A)-specific ribonuclease activity as a deadenylase subunit. Reason: Recombinant Pop2p catalytic domain degrades poly(A), supporting poly(A)-specific ribonuclease activity. Supporting Evidence: PMID:11410650 A recombinant Pop2p fragment encompassing the putative catalytic domain degrades poly(A) in vitro demonstrating that Pop2p is a nuclease |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: CAF1/Pop2p is reported in the nucleus in addition to cytoplasm. Reason: Subcellular location mapping supports nuclear localization. Supporting Evidence: GO_REF:0000044 UniProt subcellular location mapping |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: CAF1/Pop2p is a component of the major cytoplasmic deadenylase complex. Reason: Ccr4p/Pop2p form the major cytoplasmic deadenylase in yeast. Supporting Evidence: GO_REF:0000044 UniProt subcellular location mapping |
| GO:0006351 DNA-templated transcription | IEA GO_REF:0000043 | MODIFY | Summary: Broad transcription term; evidence supports a specific role in transcription elongation. Reason: CCR4-NOT contributes to transcription elongation rather than general transcription. Proposed replacements: transcription elongation by RNA polymerase II Supporting Evidence: GO_REF:0000043 UniProt keyword mapping |
| GO:0016787 hydrolase activity | IEA GO_REF:0000043 | MODIFY | Summary: Hydrolase activity is too general; Pop2p is a poly(A)-specific ribonuclease. Reason: Specific ribonuclease activity better captures Pop2p function. Proposed replacements: poly(A)-specific ribonuclease activity Supporting Evidence: GO_REF:0000043 UniProt keyword mapping |
| GO:0030014 CCR4-NOT complex | IEA GO_REF:0000002 | ACCEPT | Summary: CAF1/Pop2p is a subunit of the CCR4-NOT complex. Reason: CAF1/Pop2p is consistently identified within CCR4-NOT complex purifications. Supporting Evidence: PMID:11733989 The 1.0 MDa complex was found to contain CCR4, CAF1, NOT1-5 and two new proteins, CAF40 and CAF130 |
| GO:0046872 metal ion binding | IEA GO_REF:0000043 | MARK AS OVER ANNOTATED | Summary: Metal ion binding is a nonspecific prediction and does not add functional specificity for Pop2p. Reason: Functional annotations are better captured by specific ribonuclease activity terms. Supporting Evidence: GO_REF:0000043 UniProt keyword mapping |
| GO:0005515 protein binding | IPI PMID:11733989 Purification and characterization of the 1.0 MDa CCR4-NOT co... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:11733989 Purification and characterization of the 1.0 MDa CCR4-NOT complex identifies two novel components of the complex. |
| GO:0005515 protein binding | IPI PMID:11780629 The DEAD box helicase, Dhh1p, functions in mRNA decapping an... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:11780629 The DEAD box helicase, Dhh1p, functions in mRNA decapping and interacts with both the decapping and deadenylase complexes. |
| GO:0005515 protein binding | IPI PMID:11805826 Functional organization of the yeast proteome by systematic ... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:11805826 Functional organization of the yeast proteome by systematic analysis of protein complexes. |
| GO:0005515 protein binding | IPI PMID:11805837 Systematic identification of protein complexes in Saccharomy... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:11805837 Systematic identification of protein complexes in Saccharomyces cerevisiae by mass spectrometry. |
| GO:0005515 protein binding | IPI PMID:14759368 High-definition macromolecular composition of yeast RNA-proc... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:14759368 High-definition macromolecular composition of yeast RNA-processing complexes. |
| GO:0005515 protein binding | IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:16429126 Proteome survey reveals modularity of the yeast cell machinery. |
| GO:0005515 protein binding | IPI PMID:16554755 Global landscape of protein complexes in the yeast Saccharom... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:16554755 Global landscape of protein complexes in the yeast Saccharomyces cerevisiae. |
| GO:0005515 protein binding | IPI PMID:16715093 PUF proteins bind Pop2p to regulate messenger RNAs. | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:16715093 PUF proteins bind Pop2p to regulate messenger RNAs. |
| GO:0005515 protein binding | IPI PMID:18467557 An in vivo map of the yeast protein interactome. | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:18467557 An in vivo map of the yeast protein interactome. |
| GO:0005515 protein binding | IPI PMID:18719252 High-quality binary protein interaction map of the yeast int... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:18719252 High-quality binary protein interaction map of the yeast interactome network. |
| GO:0005515 protein binding | IPI PMID:19536198 An atlas of chaperone-protein interactions in Saccharomyces ... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:19536198 An atlas of chaperone-protein interactions in Saccharomyces cerevisiae: implications to protein folding pathways in the cell. |
| GO:0005515 protein binding | IPI PMID:21669201 Insights into the structure of the CCR4-NOT complex by elect... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:21669201 Insights into the structure of the CCR4-NOT complex by electron microscopy. |
| GO:0005515 protein binding | IPI PMID:24121231 Structure and RNA-binding properties of the Not1-Not2-Not5 m... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:24121231 Structure and RNA-binding properties of the Not1-Not2-Not5 module of the yeast Ccr4-Not complex. |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:37968396 The social and structural architecture of the yeast protein interactome. |
| GO:0005515 protein binding | IPI PMID:9504907 Dhh1p, a putative RNA helicase, associates with the general ... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:9504907 Dhh1p, a putative RNA helicase, associates with the general transcription factors Pop2p and Ccr4p from Saccharomyces cerevisiae. |
| GO:0005515 protein binding | IPI PMID:9528782 DBF2 protein kinase binds to and acts through the cell cycle... | REMOVE | Summary: Generic protein binding annotation from interaction study; too non-specific for CAF1/Pop2p function. Reason: Protein binding is uninformative here; CAF1/Pop2p roles are captured by deadenylase activity and CCR4-NOT complex membership. Supporting Evidence: PMID:9528782 DBF2 protein kinase binds to and acts through the cell cycle-regulated MOB1 protein. |
| GO:0000289 nuclear-transcribed mRNA poly(A) tail shortening | NAS PMID:11889048 Ccr4p is the catalytic subunit of a Ccr4p/Pop2p/Notp mRNA de... | ACCEPT | Summary: CAF1/Pop2p participates in poly(A) tail shortening as part of the CCR4-NOT deadenylase. Reason: Pop2p is part of the major cytoplasmic deadenylase and contributes to mRNA deadenylation. Supporting Evidence: PMID:11889048 Recent work has identified Ccr4p and Pop2p as components of the major cytoplasmic deadenylase in yeast |
| GO:0032968 positive regulation of transcription elongation by RNA polymerase II | IDA PMID:21406554 The multifunctional Ccr4-Not complex directly promotes trans... | KEEP AS NON CORE | Summary: CCR4-NOT promotes transcription elongation by RNA polymerase II. Reason: Transcription elongation regulation is a secondary role relative to CAF1/Pop2p deadenylase function. Supporting Evidence: PMID:21406554 The multifunctional Ccr4-Not complex directly promotes transcription elongation |
| GO:0043332 mating projection tip | HDA PMID:19053807 Systematic definition of protein constituents along the majo... | ACCEPT | Summary: High-throughput localization data place CAF1/Pop2p at the mating projection tip under pheromone response. Reason: Proteome-wide imaging identified proteins localized along the mating projection following pheromone treatment. Supporting Evidence: PMID:19053807 Systematic definition of protein constituents along the major polarization axis reveals an adaptive reuse of the polarization machinery in pheromone-treated budding yeast. |
| GO:0030015 CCR4-NOT core complex | IDA PMID:10490603 The CCR4 and CAF1 proteins of the CCR4-NOT complex are physi... | ACCEPT | Summary: CAF1/Pop2p is a core subunit of the CCR4-NOT complex. Reason: Complex purification and interaction data place CAF1/Pop2p within the CCR4-NOT core module. Supporting Evidence: PMID:10490603 The CAF1 protein was found to be absolutely required for CCR4 association with the NOT proteins |
| GO:0000175 3'-5'-RNA exonuclease activity | IDA PMID:11410650 The yeast POP2 gene encodes a nuclease involved in mRNA dead... | ACCEPT | Summary: Pop2p exhibits 3'-5' RNA exonuclease activity on poly(A) substrates. Pop2 belongs to the RNase D/DEDD family; structure-guided mutagenesis of the active-site residues S44 and E46 abolishes detectable RNase activity, localizing the catalysis to the Pop2 RNase D domain. Cleavage proceeds distributively. Reason: Recombinant Pop2p catalytic domain degrades poly(A) in vitro; S44A/E46A active-site mutants abolish activity. Supporting Evidence: PMID:11410650 A recombinant Pop2p fragment encompassing the putative catalytic domain degrades poly(A) in vitro demonstrating that Pop2p is a nuclease file:yeast/POP2/POP2-deep-research-falcon.md Mutation of residues **S44A and E46A** (within the DEDD-motif region described for the family/active site) abolished detectable activity in vitro, strongly linking the catalytic activity to the Pop2 RNase D domain file:yeast/POP2/POP2-deep-research-falcon.md cleavage proceeded in a **distributive** manner |
| GO:0000289 nuclear-transcribed mRNA poly(A) tail shortening | IDA PMID:11410650 The yeast POP2 gene encodes a nuclease involved in mRNA dead... | ACCEPT | Summary: CAF1/Pop2p participates in poly(A) tail shortening as part of the CCR4-NOT deadenylase. Reason: Pop2p is part of the major cytoplasmic deadenylase and contributes to mRNA deadenylation. Supporting Evidence: PMID:11410650 supports the involvement of Pop2p in mRNA deadenylation in vivo |
| GO:0000289 nuclear-transcribed mRNA poly(A) tail shortening | IMP PMID:11410650 The yeast POP2 gene encodes a nuclease involved in mRNA dead... | ACCEPT | Summary: CAF1/Pop2p participates in poly(A) tail shortening as part of the CCR4-NOT deadenylase. Reason: Pop2p is part of the major cytoplasmic deadenylase and contributes to mRNA deadenylation. Supporting Evidence: PMID:11410650 supports the involvement of Pop2p in mRNA deadenylation in vivo |
| GO:0000289 nuclear-transcribed mRNA poly(A) tail shortening | IDA PMID:11889048 Ccr4p is the catalytic subunit of a Ccr4p/Pop2p/Notp mRNA de... | ACCEPT | Summary: CAF1/Pop2p participates in poly(A) tail shortening as part of the CCR4-NOT deadenylase. Reason: Pop2p is part of the major cytoplasmic deadenylase and contributes to mRNA deadenylation. Supporting Evidence: PMID:11889048 Recent work has identified Ccr4p and Pop2p as components of the major cytoplasmic deadenylase in yeast |
| GO:0000932 P-body | IDA PMID:18611963 A role for Q/N-rich aggregation-prone regions in P-body loca... | ACCEPT | Summary: Pop2p localizes to P-bodies, consistent with its role in mRNA decay pathways. P-body accumulation of Pop2/Ccr4 is stress-dependent; deletion of CCR4 or POP2 only minorly reduces P-body formation, indicating Pop2 is recruited to but not strictly required for foci assembly. Reason: Reduced P-body accumulation of Pop2p is observed when Q/N-rich regions are deleted, supporting P-body localization. Supporting Evidence: PMID:18611963 reduced P-body accumulation of Ccr4p, Pop2p and Dhh1p after deletion of these domains file:yeast/POP2/POP2-deep-research-falcon.md Under stress, CCR4βNOT subunits including **Ccr4 and Pop2** can relocalize to **processing bodies (P-bodies)** file:yeast/POP2/POP2-deep-research-falcon.md Deletion of **CCR4 or POP2** causes only a **minor reduction** in P-body formation |
| GO:0005737 cytoplasm | IDA PMID:11889048 Ccr4p is the catalytic subunit of a Ccr4p/Pop2p/Notp mRNA de... | ACCEPT | Summary: CAF1/Pop2p is part of the major cytoplasmic deadenylase complex. Direct localization studies show Ccr4p and Caf1p reside primarily in the cytoplasm, where cytoplasmic mRNA turnover occurs. Reason: Ccr4p/Pop2p form the major cytoplasmic deadenylase in yeast. Supporting Evidence: PMID:11889048 Recent work has identified Ccr4p and Pop2p as components of the major cytoplasmic deadenylase in yeast file:yeast/POP2/POP2-deep-research-falcon.md Ccr4p and Caf1p **localize primarily to the cytoplasm** |
| GO:0006368 transcription elongation by RNA polymerase II | IMP PMID:11404327 Genetic evidence supports a role for the yeast CCR4-NOT comp... | KEEP AS NON CORE | Summary: CCR4-NOT has a role in transcription elongation by RNA polymerase II. caf1/pop2 mutants display 6-azauracil (6AU) and mycophenolic acid (MPA) sensitivity - classic hallmarks of elongation defects - and these phenotypes are rescued by excess guanine, consistent with nucleotide-pool stress on elongation rather than a core deadenylase function. Reason: Genetic evidence links CCR4-NOT components to transcription elongation phenotypes; this is a secondary role relative to the cytoplasmic deadenylase function. Supporting Evidence: PMID:11404327 Genetic evidence supports a role for the yeast CCR4-NOT complex in transcriptional elongation file:yeast/POP2/POP2-deep-research-falcon.md caf1 mutations give rise to a 6-azauracil (6AU) phenotype file:yeast/POP2/POP2-deep-research-falcon.md ccr4, caf1, and not4 deletions** confer **mycophenolic acid sensitivity** |
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