A single-stranded DNA binding protein required for mitochondrial DNA replication in S. cerevisiae is homologous to E. coli SSB.
It has previously been shown that the mitochondrial DNA (mtDNA) of Saccharomyces cerevisiae becomes thermosensitive due to the inactivation of the mitochondrial DNA helicase gene, PIF1. A suppressor of this thermosensitive phenotype was isolated from a wild-type plasmid library by transforming a pif1 null strain to growth on glycerol at the non-permissive temperature. This suppressor is a nuclear gene encoding a 135 amino acid protein that is itself essential for mtDNA replication; cells lacking this gene are totally devoid of mtDNA. We therefore named this gene RIM1 for replication in mitochondria. The primary structure of the RIM1 protein is homologous to the single-stranded DNA binding protein (SSB) from Escherichia coli and to the mitochondrial SSB from Xenopus laevis. The mature RIM1 gene product has been purified from yeast extracts using a DNA unwinding assay dependent upon the DNA helicase activity of SV40 T-antigen. Direct amino acid sequencing of the protein reveals that RIM1 is a previously uncharacterized SSB. Antibodies against this purified protein localize RIM1 to mitochondria. The SSB encoded by RIM1 is therefore an essential component of the yeast mtDNA replication apparatus.
Van Dyck
E
E
Unité de Biochimie Physiologique, Université Catholique de Louvain, Louvain-La-Neuve, Belgium.
Foury
F
F
Stillman
B
B
Brill
S J
SJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics; D004271:DNA, Fungal / Q000096:biosynthesis / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000096:biosynthesis* / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007438:Introns; D008969:Molecular Sequence Data; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid; D013489:Suppression, Genetic
D004271:DNA, Fungal; D004272:DNA, Mitochondrial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C489601:RIM101 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D004265:DNA Helicases