Involvement of Nuclear Genes in Splicing of the Mitochondrial COB Transcript in S. Cerevisiae

Abstract

The long form of the mitochondrial COB gene consists of six exons (B1 – B6), separated by five introns (bI1 – bI5). The number of known nuclear genes in yeast specifically involved in the expression of this single mitochondrial gene, is steadily increasing. To date at least four nuclear genes (CBS1, CBS2, CBP1 and CBP6) have been shown to influence the stability of the COB transcript and its translation (Dieckmann et al., 1984; Dieckmann and Tzagoloff, 1985; Rodel, 1986). Also four genes are known to be involved in the excision of single introns from these transcripts: CBP2, MRS1, NAM2 and SUP-101. CBP2 and MRS1 gene products are essential for the excision of intron bI5 and bI3, respectively (McGraw and Tzagoloff, 1983; Kreike et al., 1986; Kreike et al., 1987). NAM2 and SUP-101 are nuclear sup-pressors of splice mutations in the COB introns bI4 and bI1, respectively (Dujardin et al., 1983; Schmelzer et al., 1983).