Mechanisms of Catalysis of Human DNA Polymerases α and β

The chapter discusses a detailed analysis of the mechanisms of catalysis of DNA polymerases α and β was initially generated by the desire to develop a formal enzymological framework within which to evaluate the interactions of the polymerases with candidate replication factors in mechanistically interpretable, model assay systems and was further stimulated by two sets of prior observations: the studies of the patterns of primer-template utilization by these enzymes, and some curious and perplexing results encountered in the examination of the effects of spermidine on the reactivity of DNA polymerase α. The studies summarized in this chapter contribute substantially to the elucidation of some of the mechanisms and specific molecular signals that govern the interaction of DNA polymerases α and β with their nucleic acid substrates. These insights are of interest for at least two reasons. First, in the absence of an exploitable library of mammalian replication/repair mutants, the enzymological properties that have been documented define a mechanistic framework within which to identify and characterize putative accessory replication factors that might act either to modify primer-template structure or to modulate the inherent catalytic properties of the polymerases themselves. The mechanistic elucidation of the stimulation of DNA polymerase α by spermidine provides a prototype for studies of this sort. Second, although it is presumed that the participation of both polymerases α and β in chromosome replication and repair must involve their interaction with a number of additional proteins, the inherent properties of the purified polymerase proteins would appear to be particularly appropriate to the putative roles of these enzymes in these complex and highly regulated processes.