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Decapping is preceded by 3' uridylation in a novel pathway of bulk mRNA turnover.

Rissland OS, Norbury CJ - Nat. Struct. Mol. Biol. (2009)

Bottom Line: Second, Cid1-dependent uridylation of polyadenylated mRNAs, such as act1, hcn1 and urg1, seems to stimulate decapping as part of a novel mRNA turnover pathway.Accordingly, urg1 mRNA is stabilized in cid1Delta cells.Uridylation and deadenylation act redundantly to stimulate decapping, and our data suggest that uridylation-dependent decapping is mediated by the Lsm1-7 complex.

View Article: PubMed Central - PubMed

Affiliation: Sir William Dunn School of Pathology, University of Oxford, UK.

ABSTRACT
Both end structures of eukaryotic mRNAs, namely the 5' cap and 3' poly(A) tail, are necessary for transcript stability, and loss of either is sufficient to stimulate decay. mRNA turnover is classically thought to be initiated by deadenylation, as has been particularly well described in Saccharomyces cerevisiae. Here we describe two additional, parallel decay pathways in the fission yeast Schizosaccharomyces pombe. First, in fission yeast mRNA decapping is frequently independent of deadenylation. Second, Cid1-dependent uridylation of polyadenylated mRNAs, such as act1, hcn1 and urg1, seems to stimulate decapping as part of a novel mRNA turnover pathway. Accordingly, urg1 mRNA is stabilized in cid1Delta cells. Uridylation and deadenylation act redundantly to stimulate decapping, and our data suggest that uridylation-dependent decapping is mediated by the Lsm1-7 complex. As human cells contain Cid1 orthologs, uridylation may form the basis of a widespread, conserved mechanism of mRNA decay.

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Deadenylation and uridylation function as redundant pathways in mRNA decay(a) The percentage of decapped, adenylated urg1 sequences that contain [black] or lack [white] terminal uridyl residues is compared for RNA isolated from WT, ccr4∆, cid1∆ cells, pan2∆ cells and pan3∆ cells (n=39, 19, 19, 27 and 20 respectively). (b-d) Poly(A) tail lengths, binned into groups of ten nt, of decapped urg1 mRNAs isolated from (b) cid1∆ cells [white], (c) pan∆ cells [white] and (d) ccr4∆ cells [white] compared to those products from wild-type cells [black].
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Figure 6: Deadenylation and uridylation function as redundant pathways in mRNA decay(a) The percentage of decapped, adenylated urg1 sequences that contain [black] or lack [white] terminal uridyl residues is compared for RNA isolated from WT, ccr4∆, cid1∆ cells, pan2∆ cells and pan3∆ cells (n=39, 19, 19, 27 and 20 respectively). (b-d) Poly(A) tail lengths, binned into groups of ten nt, of decapped urg1 mRNAs isolated from (b) cid1∆ cells [white], (c) pan∆ cells [white] and (d) ccr4∆ cells [white] compared to those products from wild-type cells [black].

Mentions: The fission yeast genome encodes two additional presumptive deadenylases, namely the Pan2-Pan3 complex and PARN. The Pan2-Pan3 complex is widely conserved among eukaryotes. In budding yeast, this complex is thought to be involved in nuclear trimming of poly(A) tails and is not a major factor in mRNA decay26,28,29. In line with analogous observations in budding yeast26, in pan2∆ cells urg1 mRNA was not stabilized and had a half-life of 10.2± 0.6 minutes (p=0.40; Fig. 6d). Although PARN has a role in specific mRNA decay pathways30,31, this deadenylase is notably absent from budding yeast and Drosophila melanogaster32. S. pombe PARN appears to not be a major enzyme in mRNA turnover, as urg1 half-life in parn∆ cells did not differ significantly from that in WT (half-life of 11.4± 3.0 minutes, p=0.24; Fig. 6d). Taken together, these data demonstrate that Cid1 and Ccr4, but neither the Pan2-Pan3 complex nor PARN, are important for mRNA decay, as judged by the increased stability of urg1 transcripts in the corresponding deletion strains. Thus, we suggest that deadenylation, mediated by Ccr4, and uridylation, mediated by Cid1, function in mRNA decay pathways in fission yeast.


Decapping is preceded by 3' uridylation in a novel pathway of bulk mRNA turnover.

Rissland OS, Norbury CJ - Nat. Struct. Mol. Biol. (2009)

Deadenylation and uridylation function as redundant pathways in mRNA decay(a) The percentage of decapped, adenylated urg1 sequences that contain [black] or lack [white] terminal uridyl residues is compared for RNA isolated from WT, ccr4∆, cid1∆ cells, pan2∆ cells and pan3∆ cells (n=39, 19, 19, 27 and 20 respectively). (b-d) Poly(A) tail lengths, binned into groups of ten nt, of decapped urg1 mRNAs isolated from (b) cid1∆ cells [white], (c) pan∆ cells [white] and (d) ccr4∆ cells [white] compared to those products from wild-type cells [black].
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Figure 6: Deadenylation and uridylation function as redundant pathways in mRNA decay(a) The percentage of decapped, adenylated urg1 sequences that contain [black] or lack [white] terminal uridyl residues is compared for RNA isolated from WT, ccr4∆, cid1∆ cells, pan2∆ cells and pan3∆ cells (n=39, 19, 19, 27 and 20 respectively). (b-d) Poly(A) tail lengths, binned into groups of ten nt, of decapped urg1 mRNAs isolated from (b) cid1∆ cells [white], (c) pan∆ cells [white] and (d) ccr4∆ cells [white] compared to those products from wild-type cells [black].
Mentions: The fission yeast genome encodes two additional presumptive deadenylases, namely the Pan2-Pan3 complex and PARN. The Pan2-Pan3 complex is widely conserved among eukaryotes. In budding yeast, this complex is thought to be involved in nuclear trimming of poly(A) tails and is not a major factor in mRNA decay26,28,29. In line with analogous observations in budding yeast26, in pan2∆ cells urg1 mRNA was not stabilized and had a half-life of 10.2± 0.6 minutes (p=0.40; Fig. 6d). Although PARN has a role in specific mRNA decay pathways30,31, this deadenylase is notably absent from budding yeast and Drosophila melanogaster32. S. pombe PARN appears to not be a major enzyme in mRNA turnover, as urg1 half-life in parn∆ cells did not differ significantly from that in WT (half-life of 11.4± 3.0 minutes, p=0.24; Fig. 6d). Taken together, these data demonstrate that Cid1 and Ccr4, but neither the Pan2-Pan3 complex nor PARN, are important for mRNA decay, as judged by the increased stability of urg1 transcripts in the corresponding deletion strains. Thus, we suggest that deadenylation, mediated by Ccr4, and uridylation, mediated by Cid1, function in mRNA decay pathways in fission yeast.

Bottom Line: Second, Cid1-dependent uridylation of polyadenylated mRNAs, such as act1, hcn1 and urg1, seems to stimulate decapping as part of a novel mRNA turnover pathway.Accordingly, urg1 mRNA is stabilized in cid1Delta cells.Uridylation and deadenylation act redundantly to stimulate decapping, and our data suggest that uridylation-dependent decapping is mediated by the Lsm1-7 complex.

View Article: PubMed Central - PubMed

Affiliation: Sir William Dunn School of Pathology, University of Oxford, UK.

ABSTRACT
Both end structures of eukaryotic mRNAs, namely the 5' cap and 3' poly(A) tail, are necessary for transcript stability, and loss of either is sufficient to stimulate decay. mRNA turnover is classically thought to be initiated by deadenylation, as has been particularly well described in Saccharomyces cerevisiae. Here we describe two additional, parallel decay pathways in the fission yeast Schizosaccharomyces pombe. First, in fission yeast mRNA decapping is frequently independent of deadenylation. Second, Cid1-dependent uridylation of polyadenylated mRNAs, such as act1, hcn1 and urg1, seems to stimulate decapping as part of a novel mRNA turnover pathway. Accordingly, urg1 mRNA is stabilized in cid1Delta cells. Uridylation and deadenylation act redundantly to stimulate decapping, and our data suggest that uridylation-dependent decapping is mediated by the Lsm1-7 complex. As human cells contain Cid1 orthologs, uridylation may form the basis of a widespread, conserved mechanism of mRNA decay.

Show MeSH
Related in: MedlinePlus