ABSTRACT
DNA polymerase (pol, i.e., DNA-dependent DNA polymerase, E.C.2.7.7.7) catalyzes the addition of deoxyribonucleotides to the 3’-hydroxyl terminus of a primed double-stranded DNA molecule (Bebenek and Kunkel, 2004). The human genome encodes at least 13 pols that conduct cellular DNA synthesis (Friedberg et al., 2000). As shown in Table 11.1, eukaryotic cells reportedly contain three replicative types: pols α, δ and ε, mitochondrial pol γ and at least 11 repair types: pols β, δ, ε, ζ, η, θ, ι, κ, λ, µ and REV 1. Pols can be classied into six main groups based on their phylogenetic relationships with Escherichia coli (E. coli) pol I (family A), E. coli pol II (family B), E. coli pol III (family C), eukaryarchaeotic pol II (family D), human pol β (family X) and E. coli UmuC/DinB and eukaryotic RAD30/xeroderma pigmentosum variant (family Y) (Friedberg et al., 2000). All known eukaryotic enzymes are either family A, family B, family X, or family Y enzymes (Table 11.1). No eukaryotic homologues of family C or family D pols were detected (www.ncbi.nlm.nih.gov/) despite detailed sequence searches using the PSI-BLAST program.
