THE HUMAN DNA-REPAIR GENE, ERCC2 (XPD), CORRECTS ULTRAVIOLET HYPERSENSITIVITY AND ULTRAVIOLET HYPERMUTABILITY OF A SHUTTLE VECTOR REPLICATED IN XERODERMA-PIGMENTOSUM GROUP-D CELLS

To determine the contribution of a human DNA repair gene, ERCC2 (XPD), to mutagenesis in human cells, two ERCC2 (XPD)-transformed xeroderma pigmentosum complementation group D (XPD) cell lines with increased UV survival compared to XP6BE(SV40), the original XPD line, were studied : D6BE-ER2-2 with slightly increased UV survival; and D6BE-ER2-9 with normal UV survival. ERCC2 (XPD) antibody-reactive protein levels were elevated 4.8-fold in D6BE-ER2-2 and 17.6-fold in D6BE-ER2-9 relative t o XP6BE(SV40). DNA repair ability was assessed by measuring the abilit y of the cells to restore expression to UV-treated plasmids. Transfect ion of pRSVcat exposed to 1000 J/m(2) UV resulted in 0.3% chlorampheni col acetyltransferase activity in XP6BE(SV40) cells but 20-80% in D6BE -ER2-2, DGBE-ER2-9, and repair-proficient cells compared to untreated control plasmids. The UV hypersensitivity of the mutagenesis shuttle v ector pSP189 in XP6BE(SV40) cells was partially corrected and the UV h ypermutability and excess of G:C --> A:T mutations of pSP189 fell to t he normal range in D6BE-ER2-2 and D6BE-ER2-9 cells. However, the frequ ency of plasmids recovered with multiple base substitution mutations w as significantly reduced with XP6BE(SV40) cells and remained low in D6 BE-ER2-2 and D6BE-ER2-9 cells, when compared with the normal fibroblas ts. The human DNA excision repair gene, ERCC2 (XPD), substantially cor rected the plasmid UV hypersensitivity and UV hypermutability of xerod erma pigmentosum complementation group D cells; however, the dose resp onse relationship varied for different end points.