6 NOVEL GENES NECESSARY FOR PRE-MESSENGER-RNA SPLICING IN SACCHAROMYCES-CEREVISIAE

We have identified six new genes whose products are necessary for the splicing of nuclear pre-mRNA in the yeast Saccharomyces cerevisiae, A collection of 426 temperature-sensitive yeast strains was generated by EMS mutagenesis, These mutants were screened for pre-mRNA splicing de fects by an RNA gel blot assay, using the intron-containing CRY1 and A CT1 genes as hybridization probes, We identified 20 temperature-sensit ive mutants defective in pre-mRNA splicing, Twelve appear to be alleli c to the previously identified prp2, prp3, prp6, prp16/prp23, prp18, p rp19 or prp26 mutations that cause defects in spliceosome assembly or the first or second step of splicing, One is allelic to SNR14 encoding U4 snRNA, Six new complementation groups, prp29-prp34, were identifie d, Each of these mutants accumulates unspliced pre-mRNA at 37 degrees C and thus is blocked in spliceosome assembly or early steps of pre-mR NA splicing before the first cleavage and ligation reaction, The prp29 mutation Is suppressed by multicopy PRP2 and displays incomplete patt erns of complementation with prp2 alleles, suggesting that the PRP29 g ene product may interact with that of PRP2, There are now at least 42 different gene products, including the five spliceosomal snRNAs and 37 different proteins that are necessary for pre-mRNA splicing in Saccha romyces cerevisiae, However, the number of yeast genes identifiable by this approach has not yet been exhausted.