The Lsm2-8 complex determines nuclear localization of the spliceosomal U6 snRNA.
Lsm proteins are ubiquitous, multifunctional proteins that are involved in the processing and/or turnover of many, if not all, RNAs in eukaryotes. They generally interact only transiently with their substrate RNAs, in keeping with their likely roles as RNA chaperones. The spliceosomal U6 snRNA is an exception, being stably associated with the Lsm2-8 complex. The U6 snRNA is generally considered to be intrinsically nuclear but the mechanism of its nuclear retention has not been demonstrated, although La protein has been implicated. We show here that the complete Lsm2-8 complex is required for nuclear accumulation of U6 snRNA in yeast. Therefore, just as Sm proteins effect nuclear localization of the other spliceosomal snRNPs, the Lsm proteins mediate U6 snRNP localization except that nuclear retention is the likely mechanism for the U6 snRNP. La protein, which binds only transiently to the nascent U6 transcript, has a smaller, apparently indirect, effect on U6 localization that is compatible with its proposed role as a chaperone in facilitating U6 snRNP assembly.
Spiller
Michael P
MP
Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JR, UK.
Boon
Kum-Loong
KL
Reijns
Martin A M
MA
Beggs
Jean D
JD
D002467:Cell Nucleus / Q000737:chemistry* / Q000378:metabolism; D017353:Gene Deletion; D012315:RNA Caps / Q000502:physiology; D012342:RNA, Small Nuclear / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000502:physiology; D017411:Ribonucleoproteins, Small Nuclear / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D017381:Spliceosomes / Q000378:metabolism; D028961:beta Karyopherins / Q000378:metabolism
C088396:LHP1 protein, S cerevisiae; C493532:Lsm2 protein, S cerevisiae; C493533:Lsm8 protein, S cerevisiae; C401305:Prp24 protein, S cerevisiae; D012315:RNA Caps; D012342:RNA, Small Nuclear; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; C405486:U6 small nuclear RNA; D028961:beta Karyopherins