PURIFICATION, CDNA CLONING, AND GENE-MAPPING OF THE SMALL-SUBUNIT OF HUMAN DNA-POLYMERASE-EPSILON

HeLa DNA polymerase epsilon (pol epsilon), possibly involved in both D NA replication and DNA repair, consists of a catalytic subunit of 261 kDa and a tightly bound peptide with a relative molecular mass of 55 k Da. The cDNA of the 261-kDa polypeptide has been independently cloned, sequenced, and then overexpressed in insect cells to give a soluble, but catalytically unstable protein, suggesting that the small subunit of HeLa pol epsilon might be important for stability. HeLa pol epsilon has been isolated by immunoaffinity purification to obtain sequence i nformation which enabled the cloning of a full-length human cDNA encod ing the small subunit. The clone encoded nine proteolytic peptides obt ained from the subunit. The 59,434-Da predicated polypeptide has 26% i dentity and 44% homology to the yeast pol epsilon 80-kDa subunit, DPB2 , Using fluorescence in situ hybridization, the human pol epsilon p59 locus (DPE2) was assigned to chromosome 14q13-q21.