MITOCHONDRIAL-DNA POLYMERASES FROM YEAST TO MAN - A NEW FAMILY OF POLYMERASES

We report the sequence of a 4.5-kb cDNA clone isolated from a human me lanoma library which bears high amino acid sequence identity to the ye ast mitochondrial (mt) DNA polymerase (Mip1p). This cDNA contains a 37 20-bp open reading frame encoding a predicted 140-kDa polypeptide that is 43% identical to Mip1p. The N-terminal part of the sequence contai ns a 13 glutamine stretch encoded by a CAG trinucleotide repeat which is not found in the other DNA polymerases gamma (Pol gamma). Multiple amino acid sequence alignments with Pol gamma from Saccharomyces cerev isiae, Schizosaccharomyces pombe, Pichia pastoris, Drosophila melanoga ster, Xenopus laevis and Mus musculus show that these DNA polymerases form a family strongly conserved from yeast to man and are only loosel y related to the Family A DNA polymerases.