A detailed analysis of the yeast replication DNA polymerase, DNA pol I, is being undertaken at the molecular and genetic level. The objectives of this project are to map and clone the gene for DNA pol I, to identify subunits and accessory proteins that influence DNA pol I activity and, ultimately, to identify the proteins that regulate its activity on native DNA templates and to determine the mechanism of their interactions. Using purified DNA pol 1, we have identified several proteins that stimulate its synthetic activity. These include three different RNase H proteins, three different single-stranded DNA binding proteins (ySSBs) and a DNA-dependent ATPase (ATPase III) that possesses a helicase activity. In this year, we have studied the mechanisms of stimulation by each protein in detail. Three different ySSBs primarily prevent non-productive binding form of yeast DNA polymerase I on DNA templates, as the proteins increase neither processivity nor accuracy of DNA polymerase I reaction. On the other hand, ATPse III increases the processivity at least 2-3 fold. Furthermore, a catalitic amount of ATPase III is required for maximal stimulation of DNA polymerase I reaction strongly suggests that ATPase III interacts with DNA polymerase I.
