Polymerases for Replicating Damaged DNA

Family Y polymerases typically (but not invariably) have relatively low processivity, low catalytic efficiency, and low fidelity when copying undamaged DNA templates (Table II). The low fidelity reflects their lack of 3 exonucleolytic proofreading activity and also the intrinsically low nucleotide selectivity of the polymerase active site. X-ray crystal structures (Friedberg et al, 2001 Ling et al, 2001 Silvian et al, 2001 Trincao et al, 

Bypass of some lesions may be conducted by one polymerase that can insert bases opposite the lesion and also extend the resulting primer terminus (Fig. 5A). Other lesions may require two TLS polymerases for bypass (Fig. 5B) one for insertion and another for extension, (e.g., Pol see Chapter 6). Thus, translesion synthesis likely requires multiple switches among polymerases and perhaps between polymerases and 3 exonucleases (e.g., intrinsic to Pol b or Pol e) to allow proofreading of errors introduced by the TLS pols (Matsuda et al, 2000), thus ensuring efficient and accurate TLS. The mechanisms responsible for these enzymatic switches are under active investigation (e.g., see other chapters and also McCulloch et al, 2004 Pham et al, 2001a). Coordination of 

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