Transient complementation of xeroderma pigmentosum cells by microinjection of poly(A)⁺ RNA

An assay has been developed in which excision repair deficiency of xeroderma pigmentosum cells is transiently complemented, as measured by unscheduled DNA synthesis, by microinjection of cytoplasmic poly(A)⁺ RNA derived from HeLa cells. Four different complementation groups of xeroderma pigmentosum have been assayed. Groups A and G showed complementation, whereas groups D and F did not. Survival for cells in each of the groups subsequent to microinjection was ~75%. Approximately 10-25% of surviving cells from groups A and G were complemented, as judged by near-normal unscheduled DNA synthesis. Fractionation of cytoplasmic poly(A)⁺ RNA on a 15-30% nondenaturing sucrose gradient and subsequent microinjection of the individual fractions indicate that repair mRNAs that complement xeroderma pigmentosum groups A and G sediment of approximately 11 S and 12 S, respectively. This assay should be of great utility in the cloning and biochemical analysis of DNA repair genes.