title: Mouse CAF1 can function as a processive deadenylase/3'-5'-exonuclease in vitro but in yeast the deadenylase function of CAF1 is not required for mRNA poly(A) removal.
abstract: The mouse CAF1 (mCAF1) is an ortholog of the yeast (y) CAF1 protein, which is a component of the CCR4-NOT complex, the major cytoplasmic deadenylase of Saccharomyces cerevisiae. Although CAF1 protein belongs to the DEDDh family of RNases, CCR4 appears to be the principle deadenylase of the CCR4-NOT complex. Here, we present evidence that mCAF1 is a processive, 3'-5'-RNase with a preference for poly(A) substrates. Like CCR4, increased length of RNA substrates converted mCAF1 into a processive enzyme. In contrast to two other DEDD family members, PAN2 and PARN, mCAF1 was not activated either by PAB1 or capped RNA substrates. The rate of deadenylation in vitro by yCCR4 and mCAF1 were both strongly influenced by secondary structures present in sequences adjacent to the poly(A) tail, suggesting that the ability of both enzymes to deadenylate might be affected by the context of the mRNA 3'-untranslated region sequences. The ability of mCAF1 to complement a ycaf1 deletion in yeast, however, did not require the RNase function of mCAF1. Importantly, yCAF1 mutations, which have been shown to block its RNase activity in vitro, did not inactivate yCAF1 in vivo, and mRNAs were deadenylated in vivo at nearly the same rate as found for wild type yCAF1. These results indicate that at least in yeast the CAF1 RNase activity is not required for its in vivo function.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824, USA.
authors.forename: Palaniswamy
authors.initials: P
authors.lastname: Viswanathan
authors.forename: Takbum
authors.initials: T
authors.lastname: Ohn
authors.forename: Yueh-Chin
authors.initials: YC
authors.lastname: Chiang
authors.forename: Junji
authors.initials: J
authors.lastname: Chen
authors.forename: Clyde L
authors.initials: CL
authors.lastname: Denis
mesh_terms: D000483:Alleles; D001483:Base Sequence; D020134:Catalytic Domain; D004591:Electrophoresis, Polyacrylamide Gel; D005095:Exoribonucleases / Q000378:metabolism; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000378:metabolism; D007700:Kinetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D011061:Poly A / Q000378:metabolism; D039102:Poly(A)-Binding Proteins / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D012315:RNA Caps; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins; D012260:Ribonucleases; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013997:Time Factors
chemical_list: D005095:Exoribonucleases; D005982:Glutathione Transferase; D011061:Poly A; D039102:Poly(A)-Binding Proteins; D011506:Proteins; D012315:RNA Caps; D012333:RNA, Messenger; D012097:Repressor Proteins; D012260:Ribonucleases; D029701:Saccharomyces cerevisiae Proteins; C450100:pab1 protein, S cerevisiae; C489778:Cnot7 protein, mouse; C079009:POP2 protein, S cerevisiae