Fidelity and processivity of Saccharomyces cerevisiae DNA polymerase eta

The yeast RAD30 gene functions in error-free replication of UV-damaged DNA, and RAD30 encodes a DNA polymerase, pol eta, that has the ability to effic iently and correctly replicate past a cis-syn-thymine-thymine dimer in temp late DNA. To better understand the role of pol eta in damage bypass, we exa mined its fidelity and processivity on nondamaged DNA templates. Steady-sta te kinetic analyses of deoxynucleotide incorporation indicate that pol eta has a low fidelity, misincorporating deoxynucleotides with a frequency of a bout 10(-2) to 10(-3) Also pol eta has a low processivity, incorporating on ly a Pew nucleotides before dissociating. We suggest that pol eta's low fid elity reflects a flexibility in its active site rendering it more tolerant of DNA damage, while its low processivity limits its activity to reduce err ors.