Role of Introns in the Yeast Cytochrome- b Gene: Cis - and Trans -acting Signals, Intron Manipulation, Expression, and Intergenic Communications

Abstract

In a volume on mitochondrial genes it is appropriate to ask questions about the structure and organization (i.e., anatomy), expression and regulation (i.e., physiology), communication and integration (i.e., sociology), and speciation and phylogeny (i.e., history) of a gene. The yeast mitochondrial gene, referred to as cob or box, which specifies the amino acid sequence of cytochrome b (Slonimski and Tzagoloff 1976; Tzagoloff et al. 1976; Claisse et al. 1977; Colson et al. 1979) and controls the synthesis of cytochrome oxidase (Kotylak and Slonimski 1976; Pajot et al. 1976), is an excellent system for investigating such questions. It was shown (Slonimski et al. 1978b), confirmed, and extended (Grivell et al. 1979; Haid et al. 1979; Alexander et al. 1980; Nobrega and Tzagoloff 1980) that the gene displays a mosaic organization composed of exons and introns. Intron mutations arrest RNA splicing (Church et al. 1979; Haid et al. 1980; Halbreich et al. 1980; Van Ommen et al. 1980) and accumulate novel polypeptide chains (Claisse et al. 1978; Kreike et al. 1979; Solioz and Schatz 1979), Introns have different functions from exons because they constitute separate complementation groups (Slonimski et al. 1978a; Kochko et al. 1979; Lamouroux et al. 1980). It was proposed (Church and Gilbert 1980; Jacq et al. 1980a) that introns encode splicing proteins. This was demonstrated (Lazowska et al. 1980) for the second intron, 12; thus, the mRNA-maturase model of splicing homeostasis can be used as a paradigm of the regulation of mosaic-gene expression. The aim of this paper is...