Enzymologic Mechanism of Replicative DNA Polymerases in Higher Eukaryotes

This chapter discusses the results of enzymologic experiments performed originally with the pol-α catalytic core, subsequently with the pol- α holoenzyme, and most recently with the pol-δ catalytic core. Pol-α and pol-δ follow similar ordered sequential terreactant mechanisms of substrate recognition and binding. For both polymerases, the first substrate bound is template. This observation has two clear implications for in vivo replication. First, to initiate DNA synthesis, both enzymes would require single-stranded DNA template— that is, first substrate. Second, neither pol-α nor pol-δ should be able to fill a gap efficiently. Once template size was reduced below the necessary minimum, both enzymes would presumably lack the first substrate and would dissociate from the DNA. Comparable studies of pol-є have not yet been performed. Results of the experiments with pol-α and pol-δ have provided fundamental and presumably general information regarding the basic mechanisms of replicative DNA polymerases, as well as novel insights into the fidelity of DNA replication, the interaction of DNA polymerases with template-primers containing chemically modified or damaged bases, and the mechanism of polymerase translocation along templates.