Selective metal ion utilization contributes to the transformation of the activity of yeast polymerase η from DNA polymerization toward RNA polymerization

Abstract

ABSTRACTPolymerase eta (Polη) is a translesion synthesis DNA polymerase directly linked to cancer development. It can bypass several DNA lesions thereby rescuing DNA damage-stalled replication complexes. We previously presented evidence implicatingSaccharomyces cerevisiaePolη in transcription elongation, and identified its specific RNA extension and translesion RNA synthetic activities. However, RNA synthesis by Polη proved rather inefficient under conditions optimal for DNA synthesis. Searching for factors that could enhance its RNA synthetic activity, we have identified the divalent cation of manganese. Here we show, that manganese triggers drastic changes in the activity of Polη. It increases the efficiency of ribonucleoside incorporation into RNA by ∼400-2000-fold opposite undamaged DNA, and ∼3000 and ∼6000-fold opposite TT dimer and 8oxoG, respectively. Importantly, preference for the correct base is maintained with manganese during RNA synthesis. In contrast, activity is strongly impaired, and base discrimination almost lost during DNA synthesis by Polη with manganese. Moreover, Polη shows strong preference for manganese during RNA synthesis even at 25-fold excess magnesium concentration. Based on these, we suggest that selective metal cofactor usage plays an important role in determining the specificity of Polη during synthesis enabling it to function at both replication and transcription.