Xeroderma pigmentosum C (XPC) is a DNA repair factor essential for global genome repair (GGR) in nucleotide excision repair (NER). In the present study we screened for factors regulated by XPC after DNA damage. Ultraviolet C (UVC) irradiation-induced stress response factors were analyzed by a cDNA microarray chip system in HeLa and XP4PA-SV Ypc mutant cell lines. The principal component analysis (PCA) method was employed to identify groups of genes with similar expression patterns over time after UVC irradiation. The growth arrest and DNA damage-inducible gene gadd45, as well as a small group of other genes, was found to exhibit ail inducible expression pattern after 30 min of incubation in xpc mutants but not in HeLa cells. Subsequent studies showed that gaad45 acne expression post-UVC irradiation was also present in the GGR mutant cells xpa and xpd, but not in TCR mutant csb cells. This evidence indicates that gadd5 plays a regulatory role in GGR of NER. (C) 2003 Elsevier Science (USA). All rights reserved.