MARKER-DEPENDENT RECOMBINATION IN BACTERIOPHAGE-T4 .4. RECOMBINATIONAL EFFECTS OF ANTIMUTATOR-T4 DNA-POLYMERASE

Recombinational effects of the antimutator allele tsL42 of gene 43 of phage T4, encoding DNA polymerase, were studied in crosses between rII B mutants. Recombination under tsL42-restricted conditions differed fr om the normal one in several respects: (1) basic recombination was enh anced, especially within very short distances; (2) mismatch repair tra cts were shortened, while the contribution of mismatch repair to recom bination was not changed; (3) marker interference at very short distan ces was augmented. We infer that the T4 DNA polymerase is directly inv olved in mismatch repair, performing both excision of a nonmatched sin gle strand (by its 3' --> 5' exonuclease) and filling the resulting ga p. A pathway for the mismatch repair was substantiated; it includes se quential action of endo VII (gp49) --> 3' --> 5' exonuclease (gp43) -- > DNA polymerase (gp43) --> DNA ligase (gp30). It is argued that the m arker interference at very short distances may result from the same se quence of events during the final processing of recombinational interm ediates.