MOLECULAR-GENETIC AND BIOCHEMICAL-ANALYSIS OF BRASSICA-NAPUS PROLIFERATING CELL NUCLEAR ANTIGEN FUNCTION

A cDNA encoding the proliferating cell nuclear antigen (PCNA) from Bra ssica napus (oilseed rape) was shown to complement the lethal deletion mutation in the PCNA gene (Delta POL30) of Saccharomyces cerevisiae. We provide unequivocal evidence that the B. napus PCNA can perform all the essential functions of the yeast PCNA in DNA replication, althoug h some species-specific differences may exist. In addition, the B. nap us PCNA expressed as a fusion polypeptide with glutathione S-transfera se (GST) was shown to stimulate the activity and processivity of two d elta-like DNA polymerases from wheat in vitro. These experiments provi de direct biochemical evidence that the B. napus PCNA may function as an auxiliary factor in plant cell DNA replication.