All three SOS-inducible DNA polymerases (Pol II, Pol IV and Pol V) are involved in induced mutagenesis

Most organisms contain several members of a recently discovered class of DN A polymerases (umuC/dinB superfamily) potentially involved in replication o f damaged DNA, In Escherichia coli, only Pol V (umuDC) was known to be esse ntial for base substitution mutagenesis induced by UV light or abasic sites . Here we show that, depending upon the nature of the DNA damage and its se quence context, the two additional SOS-inducible DNA polymerases, Pol II (p olB) and Pol IV (dinB), are also involved in error-free and mutagenic trans lesion synthesis (TLS). For example, bypass of N-2-acetylaminofluorene (AAF ) guanine adducts located within the NarI mutation hot spot requires Pol II for -2 frameshifts but Pol V for error-free TLS, On the other hand, error- free and -1 frameshift TLS at a benzo(a)pyrene adduct requires both Pol IV and Pol V, Therefore, in response to the vast diversity of existing DNA dam age, the cell uses a pool of 'translesional' DNA polymerases in order to by pass the various DNA lesions.