Marker-Dependent Recombination in T4 Bacteriophage. I. Outline of the Phenomenon and Evidence Suggesting a Mismatch Repair Mechanism

Abstract

In standard crosses, some rIIB mutants of T4 phage were found to be susceptible to an extra recombination mechanism to which the other mutants were much less susceptible. The following observations were interpreted as evidence for the mismatch-repair nature of the phenomenon: (1) Marker-dependent recombination generates exclusively double exchanges at both sides of the marker. (2) Marker-dependent recombination is highly sensitive to DNA base sequence at the site of the marker and to that at the corresponding site on the chromosome of the other parent. (3) Within certain limits, the contribution of the marker-dependent mechanism to the total recombination frequency is distance-independent and thus constitutes a constant component.

Genetic recombination in bacteriophage T4: single-burst analysis of cosegregants and evidence in favor of a splice/patch coupling model.

“…We do not think that the observed correlation between double and single exchanges was caused by reiterative recombinogenic action of chromosomal tips or by some other cell-to-cell as well as chromosome-to-chromosome recombination nonrandomness. Quite the opposite, we think that there are no serious arguments against formation of patches as primary recombination products (BERGER 1965;WIEMANN 1965), the patches and, to some extent, mismatch repair being able to explain all or nearly all high negative interference (TOOMPUU and SHCHERBAKOV 1980;SHCHERBAKOV et al 1982b). The specificity of the observed correlation (between single and double exchanges) argues itself against its origin from more than random reiteration of recombinational events.…”

“…FC21 and FC47 are mutations with an opposite phase shift (minus and plus, respectively); they mutually suppress each other, so that the double mutant FC21-FC47 has rII+ phenotype: it produces wild-type plaques on Escherichia coli B and grows efficiently on Xlysogenic hosts. The origin of the T4 strains was described earlier (SHCHERBAKOV et al 1982a; SHCHERBAKOV and PLU-Bacteria: E. coli BB was used to prepare phage stocks and to determine the total titer in lysates from crosses; E. coli B GINA 199 1). served as a host in phage crosses and as the indicator strain to discern r+ and r phenotypes.…”

Marker-Dependent Recombination in T4 Bacteriophage. Ii. The Evaluation of Mismatch Repairabilities in Crosses Within Indicator Distances

“…In keeping with formula (l), we combined a large number of triads i-a-j within the limits of indicator distances. To avoid marker interference ( SHCHERBAKOV et al 1982), we used only mutations of low recombination ability as the testmarkers i and j. The characterized mutations a were either of high recombination ability (HR-mutations) with known repair regions (Figure 1) or of low recombination ability (LR-mutations).…”

“…The K-A values were calculated for all iA x Ia, aJ x Aj, and iJ X Ij crosses described in the companion paper (SHCHERBAKOV et al 1982) and averaged over the triads involving the same mutation a. The results are summarized in Table 1 and in Figure 2, diagram I, presenting the repairability values on a linear scale.…”

“…In Table 2 the IAJ frequency values are given within indicator distances determined as described in the companion paper (SHCHERBAKOV et al 1982).…”