The sole LSm complex in Cyanidioschyzon merolae associates with pre-mRNA splicing and mRNA degradation factors

dc.contributor.authorReimer, Kirsten A.
dc.contributor.authorStark, Martha R.
dc.contributor.authorAguilar, Lisbeth-Carolina
dc.contributor.authorStark, Sierra R.
dc.contributor.authorBurke, Robert D.
dc.contributor.authorMoore, Jack
dc.contributor.authorFahlman, Richard P.
dc.contributor.authorYip, Calvin K.
dc.contributor.authorKuroiwa, Haruko
dc.contributor.authorOeffinger, Marlene
dc.contributor.authorRader, Stephen D.
dc.description.abstractProteins of the Sm and Sm-like (LSm) families, referred to collectively as (L)Sm proteins, are found in all three domains of life and are known to promote a variety of RNA processes such as base-pair formation, unwinding, RNA degradation, and RNA stabilization. In eukaryotes, (L)Sm proteins have been studied, inter alia, for their role in pre-mRNA splicing. In many organisms, the LSm proteins form two distinct complexes, one consisting of LSm1-7 that is involved in mRNA degradation in the cytoplasm, and the other consisting of LSm2-8 that binds spliceosomal U6 snRNA in the nucleus. We recently characterized the splicing proteins from the red alga Cyanidioschyzon merolae and found that it has only seven LSm proteins. The identities of CmLSm2-CmLSm7 were unambiguous, but the seventh protein was similar to LSm1 and LSm8. Here, we use in vitro binding measurements, microscopy, and affinity purification-mass spectrometry to demonstrate a canonical splicing function for the C. merolae LSm complex and experimentally validate our bioinformatic predictions of a reduced spliceosome in this organism. Copurification of Pat1 and its associated mRNA degradation proteins with the LSm proteins, along with evidence of a cytoplasmic fraction of CmLSm complexes, argues that this complex is involved in both splicing and cytoplasmic mRNA degradation. Intriguingly, the Pat1 complex also copurifies with all four snRNAs, suggesting the possibility of a spliceosome-associated pre-mRNA degradation complex in the nucleus.en_US
dc.description.sponsorshipWe thank Matt Halstead and Kelly Hrywkiw for initial work on recombinant LSm protein expression. Dr. Takayuki Fujiwara shared important tips for C. merolae microscopy. Naomi Fast and Andrew MacMillan provided helpful discussions on this project. Farid Jalali (Olympus) was instrumental in helping us optimize data collection on the fluorescence microscope. We thank the members of the Rader and Oeffinger laboratories for thoughtful discussion of this work. Denis Faubert and his team in the mass spec facility at IRCM provided invaluable assistance and advice. This work was supported by an undergraduate Research Project Award from the UNBC Office of Research (K.A.R.), the Natural Sciences and Engineering Research Council (NSERC) of Canada Discovery Grant 298521 to S.D.R., NSERC Discovery Grant RGPIN-201603737 to R.D.B., NSERC Discovery Grant RGPIN 418157-12 to C.K.Y., NSERC Discovery Grant 341453-12 to R.P.F., and NSERC Discovery Grant RGPIN-2015-06586 to M.O.en_US
dc.identifier.citationReimer, K.A.; Stark, M.R.; Aguilar, L.; Stark, S.R.; Burke, R.D.; Moore, J.; … & Rader, S.D. (2017). The sole LSm complex in Cyanidioschyzon merolae associates with pre-mRNA splicing and mRNA degradation factors. RNA, 23(6), 952-967. doi: 10.1261/rna.058487.116en_US
dc.subjectCyanidioschyzon merolaeen_US
dc.subjectLSm complexen_US
dc.subjectU6 snRNAen_US
dc.subjectpre-mRNA splicingen_US
dc.subjectmRNA degradationen_US
dc.titleThe sole LSm complex in Cyanidioschyzon merolae associates with pre-mRNA splicing and mRNA degradation factorsen_US


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