Mutator mutations in bacteriophage T4 gene 32 (DNA unwinding protein)

Abstract

Bacteriophage T4 gene 32 encodes a DNA unwinding protein required for DNA replication, repair, and recombination. Gene 32 temperature-sensitive mutations enhance virtually all base pair substitution mutation rates.

Mutator and antimutator phenotypes of suppressed amber mutants in genes 32, 41, 44, 45, and 62 in bacteriophage T4

“…Although no significant effects were observed in the gene 56 mutants, the possibility still remains that a larger sampling of gene 56 mutants may demonstrate mutator or antimutator phenotypes. The elevated reversion frequencies observed for the two gene 32 mutants, amA453 and amNG461, are not unexpected in view of recent reports (3,4,12,19). The significantly lowered error frequency for the gene 32 mutant amE315 is, however, somewhat anomalous.…”

“…One may logically expect that the determination of fidelity by the gene 32 protein stems from its ability to bind to single-stranded DNA, thereby providing a suitable template (1,6,7), and/or to interact with the DNA polymerase (17,21,24). It has been observed previously that mutator, but not antimutator, phenotypes result from disturbing the function of the gene 32 protein (3,4,12,19). However, there has been some evidence to show that a decreased stabilization of the helix immediately preceding the incoming nucleotide may lower the probability of an error in replication (Bessman and Reha-Krantz, J. Mol.…”

“…In particular, mutations in T4 gene 43 (DNA polymerase) have produced increased (25) and decreased (13) mutation frequencies of as much as two orders of magnitude. Lesser effects have been seen with mutants in genes 32 (DNA unwinding protein) (3,4,12,19), 44 (ATPase) (3), and 42 (dCMP hydroxymethylase) (9,12,26). Mutations in genes 30 (ligase) and 46 and 47 (exonucleases), phenotypically characterized as DA (DNA arrest), have also yielded alterations in mutation frequency (4,5,18).…”