¹Institute for Molecular and Cellular Biology, Osaka University and CREST, Japan Science and Technology Corporation, 1-3 Yamada-Oka, Suita, Osaka 565-0871, Japan

²RIKEN (The Institute of Physical and Chemical Research), Wako-Shi, Saitama 351-0198, Japan

Correspondence to: F Hanaoka, Institute for Molecular and Cellular Biology, Osaka University, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan

The xeroderma pigmentosum variant (XP-V) is one of the most common forms of this cancer-prone syndrome. XP groups A through G are characterized by defective nucleotide excision repair, whereas the XP-V phenotype is proficient in this pathway. The XPV gene encodes DNA polymerase , which catalyzes an accurate translesion synthesis, indicating that the XPV gene contributes tumor suppression in normal individuals. Here we describe the genomic structure and chromosomal localization of the XPV gene, which includes 11 exons covering the entire coding sequence, lacks a TATA sequence in the upstream region of the transcription-initiation, and is located at the chromosome band 6p21.1-6p12. Analyses of patient-derived XP-V cell lines strongly suggested that three of four cell lines carried homozygous mutations in the XPV gene. The fourth cell line, XP1RO, carried heterozygous point mutations in the XPV gene, one of which was located at the splice acceptor site of exon 2, resulting in the omission of exon 2 from the mature mRNA. These findings provide a basis for diagnosis and therapy of XP-V patients. Oncogene (2000) 19, 4721-4728

xeroderma pigmentosum variant (XPV); DNA polymerase ; genomic structure; chromosome 6; mutation analysis; TATA-less promoter; translesion synthesis