Insertion of E. coli photoreactivating enzyme into V79 hamster cells

Abstract

Photoreactivating enzyme mediates the specific repair of UV light [220–300 nm, (UV)]-induced cyclobutyl pyrimidine dimers in DNA¹. It binds to dimer-containing DNA, and on absorption of light in the wavelength range 300–500 nm monomerizes the dimer, restoring biological activity to DNA². The specificity of the enzyme for pyrimidine dimers in DNA allows its use as an analytical tool. If UV-induced biological damage is photoreactivable, dimers are probably a major cause of that damage. Thus dimers have been implicated in producing death and mutation in prokaryotes and in simple eukaryotes³ . Although this photoreactivation test has great potential value in assessing the role of dimers in UV-induced damage in mammalian cells, its use in cultured mammalian cells has been limited by the dependence of photoreactivating enzyme levels on the cell species⁴, genotype⁵ and culture medium^6,7. We have developed a method for insertion of Escherichia coli photoreactivating enzyme into mammalian cells, and show here that the inserted bacterial enzyme can mediate photoreactivation of pyrimidine dimers in V79 rodent cells.