Expression of a cloned denV gene of bacteriophage T4 in Escherichia coli.

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Abstract
A 713-base-pair HaeII fragment from bacteriophage T4 encompassing the denV gene with its preceding promoter was cloned in a pBR322-derived positive-selection vector and introduced into a variety of DNA repair deficient uvr and rec and uvr, rec E. coli strains. The denV gene was found to be expressed, probably from its own promoter, causing pyrimidine dimer incision-deficient uvrA, uvrB, uvrC strains to be rescued by the denV gene. A uvrD (DNA helicase II) strain was also complemented, but a lesser extent. A wild-type strain did not seem to be affected at the UV doses tested. All recA, recB and recC strains tested also showed an increased UV reistance, perhaps by reinforcement of the intact uvr system in these strains. Complementation of denV- T4 strains and host-cell reactivation of .lambda. phage was also observed in denV+ E. coli strains. Equilibrium sedimentation showed that DNA repair synthesis occurred in a UV-irradiated uvrA E. coli strain carrying the cloned denV GENE. Southern blotting confirmed earlier results that the denV gene is located at 64 kilobases on the T4 map. Phage T2 (denV-) did not hybridize to a denV-specific probe.