Opposing regulation by Rev1 of DNA polymerase zeta activity on damaged versus undamaged DNA

Abstract

The Rev1 deoxycytidyl transferase functions as a scaffold protein for DNA polymerase {zeta} (Pol {zeta})-mediated translesion synthesis (TLS). Biochemical studies with yeast enzymes indicate that Rev1 plays a dual regulatory role in TLS, stimulating Pol {zeta} activity at sites of damage but inhibiting its activity on undamaged DNA. An evolutionary conserved N-terminal alpha-helical motif (M1), located 10-20 amino acids upstream of Rev1s single BRCT domain, is required for the inhibitory activity of Rev1 on undamaged DNA. Mutations in the M1 motif result in a stimulation of Pol {zeta} replication activity on both undamaged and damaged DNA. Yeast cells carrying a REV1 mutant lacking the M1 motif, show a four-fold increase in complex mutations, without significantly affecting overall spontaneous mutation rates. A catalytically inactive mutant of Rev1 still exerts these regulatory functions. However, regulation requires that Rev1 and Pol {zeta} form a stable complex, and that this complex is coordinated by the replication clamp PCNA. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/700666v2_ufig1.gif" ALT="Figure 1"> View larger version (12K): org.highwire.dtl.DTLVardef@8ed9adorg.highwire.dtl.DTLVardef@7528a3org.highwire.dtl.DTLVardef@1bf0d92org.highwire.dtl.DTLVardef@142488_HPS_FORMAT_FIGEXP M_FIG C_FIG Rev1 stimulates lesion bypass by Pol {varsigma} but inhibits Pol {varsigma} activity on undamaged DNA