A systematic screen identifies Saf5 as a link between splicing and transcription in fission yeast

Abstract

Splicing is an important step of gene expression regulation in eukaryotes, as there are many mRNA precursors that can be alternatively spliced in different tissues, at different cell cycle phases or under different external stimuli. We have developed several life constructs that allow the quantification of fission yeast splicing in vivo on intact cells, and we have compared their splicing efficiency in a wild type strain and in a prp2-1 (U2AF65) genetic background, showing a clear dependency between Prp2 and a consensus signal at 5 splicing site (5SS). To isolate novel genes involved in regulated splicing, we have crossed the reporter containing the weakest splicing rate with the Schizosaccharomyces pombe knock out collection. Among the candidate genes involved in the regulation of splicing, we have detected strong splicing defects in two of the mutants ({Delta}cwf12 and{Delta} saf5), both of them related to the NineTeen Complex (NTC). We have identified that strains with mutations in cwf12 have inefficient splicing, mainly when the 5SS differs from the consensus. However, although{Delta} saf5 cells also have some dependency on 5SS sequence, we noticed that when one intron of a given pre-mRNA was affected, the rest of the introns of the same pre-mRNA had high probabilities of being also affected. This observation points Saf5 as a link between transcription rate and splicing.