Isolation and Characterization of Pre-$tRNA^{Val}$ Splicing Mutants of Schizosaccharomyces pombe

A collection of 132 temperature sensitive (ts) mutants was generated by the chemical mutagenesis of Schizosaccharomyces pombe wild type strain and screened for tRNA splicing defects on Northern blots by hybridization with an oligonucleotide that recognizes the exon of the S. pombe tRNA^Val as a probe. We identidied 6 mutants which accumulate precursor $tRNA^{Val}$. Among them, 2 mutants exhibited remarkable morphological differences compared to wild type cells. One tRNA splicing mutant showed elongated cell shape in permissive as well as non-permissive cultures. The other mutant exhibited shortened cell morphology only in nonpermissive culture. The total RNA pattern in the splicing mutants appeared to be normal. Genetic analysis of four $tRNA^{Val}$ splicing mutants demonstrated that the mutation reside in different genes.