Genetic conservation versus variability in mitochondria: the architecture of the mitochondrial genome in the petite-negative yeast Schizosaccharomyces pombe

Abstract

The great amount of molecular information and the many molecular genetic techniques available make Schizosaccharomyces pombe an ideal model eukaryote, complementary to the budding yeast Saccharomyces cerevisiae. In particular, mechanisms involved in mitochiondrial (mt) biogenesis in fission yeast are more similar to higher eukaryotes than to budding yeast. In this review, recent findings on mt morphogenesis, DNA replication and gene expression in this model organism are summarised. A second aspect is the organisation of the mt genome in fission yeast. On the one hand, fission yeast has a strong tendency to maintain mtDNA intact; and, on the other hand, the mt genomes of naturally occurring strains show a great variability. Therefore, the molecular mechanisms behind the susceptibility to mutations in the mtDNA and the mechanisms that promote sequence variations during the evolution of the genome in fission yeast mitochondria are discussed.

Transcription and RNA-processing in fission yeast mitochondria

“…Contrary to baker's yeast, its circular-mapping mitochondrial genome is very stable, relatively small, and devoid of long repetitive sequences in intergenic regions (for recent reviews, see Bullerwell et al 2003;Schäfer 2003). We demonstrate that fission yeast mitochondrial transcription and RNA-processing and regulation differ significantly from the budding yeast S. cerevisiae.…”

“…The degradosome is a protein complex with both the 3Ј-5Ј exoribonuclease Dss1p and the RNA helicase Suv3p Dziembowski et al 1998Dziembowski et al , 2003. RNA maturation and turnover are also controlled by several RNA-stabilizing proteins and translation activator proteins that bind to the 5Ј-UTL of mitochondrial RNAs (Wiesenberger et al 1995;Wiesenberger and Fox 1997;Green-Willms et al 1998;Chen et al 1999;Islas-Osuna et al 2002, 2003. Likewise, the 55-kDa RNA dodecamer sequence-binding protein (DBP) recognizes a dodecamer sequence in 3Ј-UTRs (Li and Zassenhaus 1999).…”

Yeast PPR proteins, watchdogs of mitochondrial gene expression

“…12 Thus, we would expect to find a PPR protein that would interact with rnpB to form the S. pombe RNase P. The newly identified Ppr10 is a possible candidate, it is a much smaller protein than Rpm2 from S. cerevisiae, but this might be because it is only involved in mitochondrial RNA processing. Alternatively, another as yet unidentified PPR protein could be the bona fide partner of rnpB.…”

“…1). The main difference in the coding capacity of these genomes is the number of introns (up to 13 in S. cerevisiae mtDNA 11 and up to four in S. pombe mtDNA 12 ), some of which encode maturases that are necessary for splicing; however, to date none of the yeast PPR proteins have been convincingly implicated in splicing per se.…”

Bot1p Is Required for Mitochondrial Translation, Respiratory Function, and Normal Cell Morphology in the Fission Yeast Schizosaccharomyces pombe

“…In S. pombe mitochondrial protein translation is regulated by the guanine nucleotide exchange factor EF-Ts, conserved in higher eukaryotes, which controls the translation elongation factor EF-Tu (7). S. pombe is a petite-negative yeast and, similarly to mammalian cells, cannot survive the loss of mtDNA and mitochondrial protein synthesis (36).…”