Identification of a new human CYP2A gene fragment with close linkage to CYP2GP1

Human genomic libraries were screened to identify CYP2G-related cytochrome P450 genes. A genomic fragment comprising exons 7 through 9 of CYP2GP1 and exons 6 through 9 of a previously unidentified CYP2A gene, designated CYP2A 7P2, was isolated from an EMBL3 library; the two genes were arranged in out ward opposite directions with about 8 kbp of intervening sequence. The same structure was also detected in a bacteriophage P1 clone, which contained a full-length CYP2GP1 gene, exons 6 through 9 of CYP2A7P2, and the CYP2B7 ge ne. However, additional CYP2A-related exons as well as other CYP2A genes, C YP2A7P1, CYP2B6, CYP2F1, and CYP2GP2 were not detected. These results indic ate that CYP2A7P2 is located near CYP2B7 in the middle of the CYP2A2B-2F ge ne cluster on chromosome 19. Furthermore, an analysis of CYP2A sequence ali gnment suggests that CYP2A7P2 may be derived from the same ancestral gene t hat gave rise to CYP2A7P1, which was corrupted by a large insertion at intr on 5.