Characterization of a new DNA polymerase from Schizosaccharomyces pombe: a probable homologue of the Saccharomyces cerevisiae DNA polymerase gamma.

Mitochondrial (mt) DNA replication is carried out by the nuclear-encoded DNA polymerase-gamma (Pol-gamma). We have cloned a new DNA polymerase-encoding gene from Schizosaccharomyces pombe (Sp), which we believe encodes the homologue of the Saccharomyces cerevisiae (Sc) mt DNA polymerase (MIP1). The putative Sp pol gamma gene expressed a transcript of approx. 4-kb that contained a 3-kb open reading frame encoding a polypeptide of 1018 amino acids (aa) (116 kDa). This Sp Pol-gamma is 48% identical to the Sc MIP1 and contains uniquely conserved regions not found in the bacterial PolI-type DNA polymerases. The most notable difference between these two proteins is that the MIP1 product has a 236-aa C-terminal region beyond motif C that is not found in Sp Pol-gamma. Chromosomal mapping and genomic sequencing of the Sp pol gamma places this gene on chromosome III downstream from the triose phosphate isomerase-encoding gene.