INTERSPECIES DNA-POLYMERASE-DELTA CHIMERAS ARE FUNCTIONAL IN SACCHAROMYCES-CEREVISIAE

The catalytic subunits of DNA polymerase delta of Schizosaccharomyces pombe and Saccharomyces cerevisiae share over 50% identity. The capabi lity of S. pombe DNA polymerase delta to complement two thermosensitiv e mutants of S. cerevisiae was studied in vivo and it was determined t hat complementation was allele dependent. However, DNA polymerase delt a from S. pombe did not restore growth of a S. cerevisiae strain conta ining a disrupted chromosomal copy of the POW gene that encodes DNA po lymerase delta. To identify the regions of DNA polymerase delta respon sible for species-specific interactions, we constructed different chim eras with S. cerevisiae and S. pombe DNA polymerase delta genes. The g rowth of a S. cerevisiae strain with a disrupted chromosomal POL3 gene was studied after transformation with plasmids expressing different c himeras. A 1254-bp region located in the 3' region of the S. cerevisia e POL3 gene is responsible for species-specific functions.