Cdm1, the smallest subunit of DNA polymerase d in the fission yeast Schizosaccharomyces pombe , is non-essential for growth and division

Highly purified DNA polymerase δ from the fission yeast Schizosaccharomyces pombe is a complex of at least four distinct subunits. Genes encoding three of these (pol3 + /cdc6 + , cdc1 + and cdc27 + ) have been characterised previously. Here we describe the isolation and characterisation of cdm1 + , the gene encoding the smallest (22kDa) subunit of the Pol δ complex. Over-expression of cdm1 + , which encodes a 160 amino-acid protein with no significant sequence similarity to proteins in current databases, is able to rescue cells carrying temperature-sensitive mutations in either pol3 + /cdc6 + , cdc1 + or cdc27 + . Cells deleted for cdm1 + are viable, indicating that cdm1 + is non-essential for mitotic growth, and are no more sensitive to a variety of DNA replication inhibitors and DNA damaging agents than are wild-type cells. In addition, over-expression of cdm1 + suppresses the temperature-sensitive cdc24-M38 mutant suggesting that cdc24 + may also have a role in DNA polymerase δ function.