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. Received: 14 June / 10 August 1998