DNA-POLYMERASE-DELTA ISOLATED FROM SCHIZOSACCHAROMYCES-POMBE CONTAINS5 SUBUNITS

DNA polymerase delta (pol delta) plays an essential role in DNA replic ation, repair, and recombination. We have purified pol delta from Schi zosaccharomyces pombe more than 10(3)-fold and demonstrated that the p olymerase activity of purified S. pombe pol delta is completely depend ent on proliferating cell nuclear antigen and replication factor C. SD S/PAGE analysis of the purified fraction indicated that the pol delta complex consists of Five subunits that migrate with apparent molecular masses of 125, 55, 54, 42, and 22 kDa. Western blot analysis indicate d that the 125, 55, and 54 kDa proteins are the large catalytic subuni t (Pol3), Cdc1, and Cdc37, respectively. The identity of the other two subunits, p42 and p22, was determined following proteolytic digestion and sequence analysis of the resulting peptides. The peptide sequence s derived from the p22 subunit indicated that this subunit is identica l to Cdm1, previously identified as a multicopy suppressor of the temp erature-sensitive cdc1-P13 mutant, whereas peptide sequences derived f rom the p42 subunit were identical to a previously uncharacterized ORF located on S. pombe chromosome 1.