Mutations in the v gene of bacteriophage T4 are associated with a marked increase in sensitivity to killing by UV radiation at 254 nm, but not to a variety of other forms of base damage to DNA1-4. Early studies from this laboratory provided evidence for a role of the v gene in the excision of pyrimidine dimers (PD) from DNA. Specifically, it was shown that extracts of T4v+-infected Esherichia coli catalyse the formation of single-strand breaks (nicks) and/or alkali-labile sites in UV-irradiated duplex DNA5. Comparable hydrolysis of phosphodiester bonds is not observed with extracts of E. coli infected with the mutant T4v1, (ref. 5). The product of the v gene has been extensively purified in a number of laboratories6-9; however, convincing evidence of purification to physical homogeneity has not yet been presented.
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