Isolation of a new spliceosome mutant with cell cycle defects by a novel conditional screening in S. pombe

Abstract

Conditional screenings have so far identified hundreds of mutants in many biological processes that allow the study of loss-of-function under the restrictive condition, but also the propagation and genetic crosses of these strains under the permissive condition. Although drug sensitivity mutants have been isolated, the most spread condition used is temperature. We have searched for formamide sensitive mutants, a novel conditionality in S. pombe, that display cell cycle defects. Among others, we have identified one mutation in the conserved spliceosome component cwf15, that allows growth in normal conditions but it blocks cell cycle progression in the presence of formamide. This mutation (cwf15.32Fs) consists of 13 nucleotides direct duplication that generates a premature stop codon and thus a C-terminal truncated protein. Cwf15 (Complexed with cdc5 protein 15) is an essential and evolutionary conserved splicing factor from yeast to humans. It has been shown to physically interact to other spliceosome components but no further characterization has been done. Here we characterize cwf15.32Fs cell cycle defects and test for genetic interactions with other splicing mutants.