DNA repair characteristics and mutability of the UV-sensitive V79 Chinese hamster cell mutant V-B11 (complementation group 7)

Abstract

The V79 Chinese hamster cell mutant V-B11 has previously been assigned to a new complementation group (group 7) of UV-sensitive rodent mutants. The D₁₀ for cell survival is 6J/m² for V-B11, compared with ˜15J/m² for the parental V79 cell line. The removal of (6–4) photoproducts from the genome overall is not impaired in V-B11, and the level of unscheduled DNA synthesis measured 2 h after UV irradiation is similar to that observed in the parental V79 cells. DNA repair replication measured as a function of UV dose is ˜50% reduced in V-B11 in comparison with V79, when measured during the first 6 h after UV irradiation. Furthermore, in V-B11 the rate of cyclobutane dimer removal from the HPRT gene is slower than in wild-type cells. Despite the observed defects no effect on the UV-induced frequency of mutants at two loci: Na⁺/K⁺-ATPase and HPRT was found in V-B11 cells. The properties of V-B11 are compared with those of other UV-sensitive mutants.