Repair of DNA Base-pair Mismatches in Extracts of Escherichia coli

Abstract

Occurrence of allelic differences within the heteroduplex region of recombination intermediates corresponds to the presence of one or more mismatched base pairs (for reviews, see Radding 1978; Stahl 1979). Rectification of such mismatches, prior to resolution of the recombinant molecule by replication, has been invoked to explain a number of marker effects associated with recombination. For example, gene conversion may reflect reduction of mismatches to homozygosity (Holliday 1964; Whitehouse and Hastings 1965; Meselson and Radding 1975), although alternate explanations for this phenomena have also been proposed (Szostak et al. 1983). Mismatch repair is also the favored explanation for marker discrimination observed in pneumococcal transformation (Ephrussi-Taylor and Gray 1966; Tiraby and Fox 1973; Lacks et al. 1982; Claverys et al. 1983), and for intragenic marker effects and localized negative interference in Escherichia coli (Norkin 1970; White and Fox 1974). In addition, mismatch correction by an excision-repair mechanism can account for genetic...