Project description:Three shuttling SR-like proteins exist in Saccharomyces cerevisiae, Npl3, Gbp2 and Hrb1, that are involved in the nuclear export of mRNAs. In a screen for genes that regulate the export of Gbp2, we identified novel mutants of the splicing factors PRP8 and PRP17 that lead to severe mislocalization defects for Gbp2 and Hrb1, but not Npl3. Microarray and qRT-PCR analyses show that Gbp2 and Hrb1 preferentially bind to transcripts derived from intron-containing genes. Moreover, in contrast to Npl3, Gbp2 and Hrb1 show genetic and physical interactions with late splicing factors such as Prp17 and Prp43. Further, RNA co-immunoprecipitation experiments reveal that, unlike Npl3, association of Gbp2 and Hrb1 with the mRNA requires splicing, and this in turn is required for their Mex67 recruitment. We propose a model in which Gbp2 and Hrb1 are attached to the mRNAs at late stages of splicing to promote the subsequent export of spliced mRNAs. keyword: RIP-chip RNA-IP of endogenously expressed 3-fold C-terminal myc-tagged Gbp2 and Hrb1 in S288C background cells was each performed once in cells grown to a density of 4x10^7 cells/ml and hybridized against a total (input) RNA reference.
Project description:Using RNA-Seq analysis of nonsense-mediated mRNA decay (NMD) mutant strains, we show that many Saccharomyces cerevisiae intron-containing genes exhibit usage of alternative splice sites, but most transcripts generated by splicing from these sites are non-functional because they introduce premature termination codons leading to transcript degradation by NMD. Analysis of splicing mutants combined with NMD inactivation revealed the role of specific splicing factors in governing the use of these alternative splice sites and identified novel functions for Prp17p in enhancing the use of branchpoint-proximal upstream 3’ splice sites and for Prp18p in suppressing the usage of a non-canonical AUG 3’-splice site. The use of non-productive alternative splice sites can limit the expression of some transcripts and can be increased in stress conditions in a promoter-dependent manner, contributing to the down-regulation of genes during stress. These results reveal that alternative splicing is frequent in S.cerevisiae but masked by RNA degradation and that the use of alternative splice sites is mostly aimed at controlling transcript levels rather than increasing proteome diversity.
Project description:Using RNA-Seq analysis of nonsense-mediated mRNA decay (NMD) mutant strains, we show that many Saccharomyces cerevisiae intron-containing genes exhibit usage of alternative splice sites, but most transcripts generated by splicing from these sites are non-functional because they introduce premature termination codons leading to transcript degradation by NMD. Analysis of splicing mutants combined with NMD inactivation revealed the role of specific splicing factors in governing the use of these alternative splice sites and identified novel functions for Prp17p in enhancing the use of branchpoint-proximal upstream 3M-bM-^@M-^Y splice sites and for Prp18p in suppressing the usage of a non-canonical AUG 3M-bM-^@M-^Y-splice site. The use of non-productive alternative splice sites can limit the expression of some transcripts and can be increased in stress conditions in a promoter-dependent manner, contributing to the down-regulation of genes during stress. These results reveal that alternative splicing is frequent in S.cerevisiae but masked by RNA degradation and that the use of alternative splice sites is mostly aimed at controlling transcript levels rather than increasing proteome diversity. mRNA-Seq profiling of 3 mutants in the nonsense-mediated mRNA decay pathway and wildtype yeast
Project description:Pre-mRNA splicing is vital for the proper function and regulation of eukaryotic gene expression. Saccharomyces cerevisiae has been used as a model organism for studies of RNA splicing because of the striking conservation of the spliceosome and its catalytic activity. Nonetheless, there are relatively few annotated alternative splice forms, particularly when compared to higher eukaryotes. Here, we describe a method to combine large scale RNA sequencing data to accurately discover novel splice isoforms in Saccharomyces cerevisiae. Using our method, we find extensive evidence for novel splicing of annotated intron-containing genes as well as genes without previously annotated introns and splicing of transcripts that are antisense to annotated genes. By incorporating several mutant strains at varied temperatures, we find conditions which lead to differences in alternative splice form usage. Despite this, every class and category of alternative splicing we find in our datasets is found, often at lower frequency, in wildtype cells under normal growth conditions. Together, these findings show that there is widespread splicing in Saccharomyces cerevisiae.