Cloning of the cDNAs for the small subunits of bovine and human DNA polymerase delta and chromosomal location of the human gene (POLD2).

cDNAs encoding the small subunit of bovine and human DNA polymerase delta have been cloned and sequenced. The predicted polypeptides, 50,885 and 51,289 Daltons, respectively, are 94% identical, similar to the catalytic subunits. The high degree of conservation of the polypeptides suggests an essential function for the small subunit in the heterodimeric core enzyme. Although the catalytic subunit of DNA polymerase delta shares significant homology with those of the herpes virus family of DNA polymerases, the small subunit of mammalian DNA polymerase delta is not homologous to the small subunit of either herpes simplex virus type 1 DNA polymerase (UL42 protein) or the Epstein-Barr virus DNA polymerase (BMRF1 protein). Searches of the protein databases failed to detect significant homology with any protein sequenced thus far. PCR analysis of DNA from a panel of human-hamster hybrid cell lines localized the gene (POLD2) for the small subunit of DNA polymerase delta to human chromosome 7.