Location of transcriptional control signals and transfer RNA sequences in Torulopsis glabrata mitochondrial DNA.

Abstract

Determination of sequences from the nine regions separating the large genes in the 19‐kbp mitochondrial DNA from Torulopsis glabrata has led to the identification of 23 tRNA genes and to the recognition of two types of short repeated sequence implicated in mitochondrial genome expression. The two short repeated sequences are a nonanucleotide motif, 5′‐TATAAGTAA‐3′ and a dodecanucleotide motif, 5′‐TATAATATTCTT‐3′. By RNA sequence determination it has been found that primary transcripts of the small and large rRNAs commence at the 3′ penultimate adenine of the nonanucleotide sequence. This motif has also been found in the DNA sequence upstream from f‐methionine, phenylalanine, leucine, tyrosine and glycine tRNAs, cytochrome oxidase subunit 2 and ATPase subunit 9. The dodecanucleotide sequence is found at least once in each of the nine regions between the large genes. Determination of the 3′ ends of the small and large rRNAs has shown their location to be 8 and 23 nucleotides downstream from the dodecanucleotide sequence. This motif is thought to be involved in signalling processing of polycistronic transcripts. Such transcripts are invoked to account for the production of mRNAs for cytochrome b, cytochrome oxidase subunits 1 and 3, and the joint mRNA for ATPase subunits 8 and 6 genes that lack an adjacent upstream nonanucleotide transcription initiation signal sequence. Processing of polycistronic transcripts at tRNA sequences is also implicated in the formation of mature mRNAs. From the position of tRNA genes relative to the nonanucleotide motif it appears that clusters of these genes are co‐transcribed with downstream sequences for cytochrome oxidase subunits 1 and 3.

NADH dehydrogenase subunit genes in the mitochondrial DNA of yeasts

“…In many yeasts so far studied, including those carrying a linear mtDNA (18), the mitochondrial genome uses a common signal, ATATAAGTA (8,16,41,57), or more generally (A/C)TA(T/A)A(A/C)G(Af/C)(A/T) (A/G) (33), that marks the transcriptional start sites. Such signals were not found in C. parapsilosis mtDNA.…”

Linear mitochondrial DNAs of yeasts: closed-loop structure of the termini and possible linear-circular conversion mechanisms.

“…In S. cerevisiae mitochondria, transcription generally starts at the sequence ATATAAGTA or its close variants (34). In other yeast species (K. lactis [34] and Candida glabrata [6]) also, this motif seems to be commonly used for transcription of rRNA, tRNA, and mRNA as well as for transcription at the replication origins. In P. pijperi mtDNA, this motif was found in the 5' flanking region of a tRNA gene cluster (EMBL accession number X66593) and in W. mrakii before the genes coding for cytochrome oxidase subunit II (12,18,36).…”

Mitochondrial RNase P RNAs in ascomycete fungi: Lineage-specific variations in RNA secondary structure

“…Additional rnpB genes have been identified by sequence similarity in mtDNAs of numerous budding yeasts (T. glabrata, Clark-Walker et al 1985; Saccharomycopsis fibuligera, Wise and Martin 1991a; Kluyveromyces lactis, Wilson et al 1989; Saccharomyces exiguus, Wise and Martin 1991b;Saccharomyces douglasii;Ragnini et al 1991; Saccharomyces chevalieri, Saccharomyces ellipsoideous, and Saccharomyces diastaticus, Sbisa et al 1996;and Saccharomyces castellii, Petersen et al 2002), the protist Reclinomonas americana , and the prasinophyte green alga N. olivacea (Turmel et al 1999), but not in the mtDNAs of plants, animals, a great number of protists, or nonascomycete fungi . From an evolutionary standpoint, it is puzzling that the occurrence of mitochondrially encoded rnpB genes is so patchy.…”