The small subunits of human and mouse DNA polymerase ε are homologous to the second largest subunit of the yeast Saccharomyces cerevisiae DNA polymerase ε

Human DNA polymerase ε is composed of a 261 kDa catalytic polypeptide and a 55 kDa small subunit of unknown function. cDNAs encoding the small subunit of human and mouse DNA polymerase ε were cloned. The predicted polypeptides have molecular masses of 59.469 and 59.319 kDa respectively and they are 90% identical. The human and mouse polypeptides show 22% identity with the 80 kDa subunit of the five subunit DNA polymerase ε from the yeast Saccharomyces cerevisiae. The high degree of conservation suggests that the 55 kDa subunit shares an essential function with the yeast 80 kDa subunit, which was earlier suggested to be involved in S phase cell cycle control in a pathway that is able to sense and signal incomplete replication. The small subunits of human and mouse DNA polymerase ε also show homology to the C-terminal domain of the second largest subunit of DNA polymerase α. The gene for the small subunit of human DNA polymerase ε (POLE2) was localized to chromosome 14q21–q22 by fluorescence in situ hybridization.