Restoration of u.v.-induced excision repair in Xeroderma D cells transfected with the denV gene of bacteriophage T4

The heritable DNA repair defect in human Xeroderma D cells, resulting in failure to incise at u.v. light-induced pyrimidine dimers, has been partially but stably corrected by transfection of immortalised cells with the denV pyrimidine dimer glycosylase gene of bacteriophage T4. Transfectants selected either for a dominant marker on the mammalian vector carrying the prokaryotic gene or for dominant marker plus resistance to killing by u.v. light, were shown to express the denV gene to varying degrees. denV expression results in significant phenotypic change in the initially repair-deficient, u.v.-hypersensitive cells. Increased resistance to u.v. light and more rapid recovery of replicative DNA synthesis following u.v. irradiation were correlated with improved repair DNA synthesis and with a novel dimer incision capability present in denV transfected Xeroderma cells but not as evident in transfected normal cells. Most transfectants contain a single integrated copy of the denV gene; increase in denV copy number does not result in either increased gene expression or enhanced survival to u.v. light. Results show that expression of a heterologous prokaryotic repair gene can partially compensate for the genetic defect in a human Xeroderma D cell. (author)