title: The Ccr4a (CNOT6) and Ccr4b (CNOT6L) deadenylase subunits of the human Ccr4-Not complex contribute to the prevention of cell death and senescence.
abstract: A key step in cytoplasmic mRNA degradation is the shortening of the poly(A) tail, which involves several deadenylase enzymes. Relatively little is known about the importance of these enzymes for the cellular physiology. Here we focused on the role of the highly similar Ccr4a (CNOT6) and Ccr4b (CNOT6L) deadenylase subunits of the Ccr4-Not complex. In addition to a role in cell proliferation, Ccr4a and Ccr4b play a role in cell survival, in contrast to the Caf1a (CNOT7) and Caf1b (CNOT8) deadenylase subunits or the CNOT1 and CNOT3 noncatalytic subunits of the Ccr4-Not complex. Underscoring the differential contributions of the deadenylase subunits, we found that knockdown of Caf1a/Caf1b or Ccr4a/Ccr4b differentially affects the formation of cytoplasmic foci by processing-body components. Furthermore, we demonstrated that the amino-terminal leucine-rich repeat (LRR) domain of Ccr4b influenced its subcellular localization but was not required for the deadenylase activity of Ccr4b. Moreover, overexpression of Ccr4b lacking the LRR domain interfered with cell cycle progression but not with cell viability. Finally, gene expression profiling indicated that distinct gene sets are regulated by Caf1a/Caf1b and Ccr4a/Ccr4b and identified Ccr4a/Ccr4b as a key regulator of insulin-like growth factor-binding protein 5, which mediates cell cycle arrest and senescence via a p53-dependent pathway.
authors.affiliation: School of Pharmacy and Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: Saloni
authors.initials: S
authors.lastname: Mittal
authors.forename: Akhmed
authors.initials: A
authors.lastname: Aslam
authors.forename: Rachel
authors.initials: R
authors.lastname: Doidge
authors.forename: Rachel
authors.initials: R
authors.lastname: Medica
authors.forename: G Sebastiaan
authors.initials: GS
authors.lastname: Winkler
mesh_terms: D002453:Cell Cycle / Q000502:physiology; D016923:Cell Death / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D016922:Cellular Senescence / Q000502:physiology*; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D055785:Gene Knockdown Techniques; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2 / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D054398:Receptors, CCR4 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012260:Ribonucleases / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: C515354:CCR4 protein, human; C528690:CNOT1 protein, human; C466622:CNOT3 protein, human; C489780:CNOT8 protein, human; D018969:Insulin-Like Growth Factor Binding Proteins; D046912:Multiprotein Complexes; C539882:NR4A2 protein, human; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D021122:Protein Subunits; D034741:RNA, Small Interfering; D054398:Receptors, CCR4; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C521732:CNOT6L protein, human; D005095:Exoribonucleases; D012260:Ribonucleases; C534418:cNOT6 protein, human