ALLELISM OF PSO4 AND PRP19 LINKS PRE-MESSENGER-RNA PROCESSING WITH RECOMBINATION AND ERROR-PRONE DNA-REPAIR IN SACCHAROMYCES-CEREVISIAE

The radiation-sensitive mutant pso4-1 of Saccharomyces cerevisiae show s a pleiotropic phenotype, including sensitivity to DNA cross-linking agents, nearly blocked sporulation and reduced mutability. We have clo ned the putative yeast DNA repair gene PSO4 from a genomic library by complementation of the blocked UV-induced mutagenesis and of sporulati on in diploids homozygous for psp4-1, Sequence analysis revealed that gene PSO4 consists of 1512 bp located upstream of UBI4 on chromosome X II and encodes a putative protein of 56.7 kDa. PSO4 is allelic to PRP1 9, a gene encoding a spliceosome-associated protein, but shares no sig nificant homology with other yeast genes, Gene disruption with a destr oyed reading frame of our PSO4 clone resulted in death of haploid cell s, confirming the finding that PSO4/PRP19 is an essential gene, Thus, PSO4 is the third essential DNA repair gene found in the yeast S. cere visiae.