Nuclear pre-mRNA decapping and 5' degradation in yeast require the Lsm2-8p complex.
Previous analyses have identified related cytoplasmic Lsm1-7p and nuclear Lsm2-8p complexes. Here we report that mature heat shock and MET mRNAs that are trapped in the nucleus due to a block in mRNA export were strongly stabilized in strains lacking Lsm6p or the nucleus-specific Lsm8p protein but not by the absence of the cytoplasmic Lsm1p. These nucleus-restricted mRNAs remain polyadenylated until their degradation, indicating that nuclear mRNA degradation does not involve the incremental deadenylation that is a key feature of cytoplasmic turnover. Lsm8p can be UV cross-linked to nuclear poly(A)(+) RNA, indicating that an Lsm2-8p complex interacts directly with nucleus-restricted mRNA. Analysis of pre-mRNAs that contain intronic snoRNAs indicates that their 5' degradation is specifically inhibited in strains lacking any of the Lsm2-8p proteins but Lsm1p. Nucleus-restricted mRNAs and pre-mRNA degradation intermediates that accumulate in lsm mutants remain 5' capped. We conclude that the Lsm2-8p complex normally targets nuclear RNA substrates for decapping.
Kufel
Joanna
J
Wellcome Trust Centre for Cell Biology, King's Buildings, The University of Edinburgh, Edinburgh EH9 3JR, United Kingdom.
Bousquet-Antonelli
Cecile
C
Beggs
Jean D
JD
Tollervey
David
D
D002467:Cell Nucleus / Q000378:metabolism*; D006358:Hot Temperature; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011061:Poly A / Q000235:genetics / Q000378:metabolism; D012315:RNA Caps / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism*; D022821:RNA Splice Sites / Q000235:genetics; D020871:RNA Stability; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
C493532:Lsm2 protein, S cerevisiae; C493533:Lsm8 protein, S cerevisiae; D046912:Multiprotein Complexes; D012315:RNA Caps; D012322:RNA Precursors; D022821:RNA Splice Sites; D012331:RNA, Fungal; D017411:Ribonucleoproteins, Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; D011061:Poly A