Control of Translesion Synthesis and Mutagenesis

DNA damage-induced mutagenesis is tightly controlled by the SOS regulatory system. Eukaryotes, on the other hand, do not contain a similar SOS response system. Nevertheless, translesion synthesis and base damage-induced mutagenesis are controlled in eukaryotic cells at two levels. First, the bypass polymerases are controlled to a low concentration in cells. Second, the extent by which translesion synthesis contributes to damage tolerance is controlled in cells. 

10a AP Sites. AP sites are a major type of spontaneous DNA lesions, although they can also be induced by many environmental agents. AP sites are noncoding. Hence, translesion synthesis of an AP site by any polymerase is error-prone. Consequently, AP sites are highly mutagenic. In E. coli, translesion synthesis of AP sites results in preferential incorporation of A opposite the lesion. Such biased A insertions do not appear to be the case in mammals. Insertions of all four bases opposite AP sites have been detected in cultured mammalian cells. 

In yeast cells, C is predominantly inserted opposite AP sites, which is dependent on the Revl and Pol function. The Revl dCMP transferase is efficient in inserting 

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