Received for publication November 29, 2005.
Revised February 9, 2006.
Accepted for publication February 27, 2006.

A common regulatory region functions bi-directionally in transcriptional activation of the human CYP1A1 and CYP1A2 genes

Abstract

The human CYP1A1 and CYP1A2 genes on chromosome 15 are orientated head-to-head and separated by 23 kb intergenic spacer region. Thus the possibility exists for sharing common regulatory elements contained in the spacer region responsible for transcriptional activation and regulation of the CYP1A1 and CYP1A2 genes. In the present study, a reporter gene construct containing -22.4 kb of the 5^' -flanking region of the CYP1A2 gene was found to support -naphthoflavone (BNF) and 3- methylchoranthrene (3-MC)-mediated transcriptional activation. The responsive region was also functional in directing activation of the CYP1A1 promoter, indicating that the region works bi-directionally to govern transcriptional activation of both the CYP1A1 and CYP1A2. To simultaneously evaluate transcriptional activation of both genes, a dual reporter vector was developed in which the spacer region was inserted between two different reporter genes, firefly luciferase and secreted alkaline phosphatase. Transient transfection of the dual reporter vector in HepG2 cells revealed increases in both reporter activities after exposure of the cells to BNF and 3-MC. Deletion studies of the spacer region indicated that a region from -464 to -1829 of the CYP1A1 gene works bi-directionally to enhance the transcriptional activation of not only CYP1A1 but also CYP1A2. In addition, a negative bidirectional regulatory region was found existing from - 18909 to -21992 of the CYP1A1 gene. These data established that induction of human CYP1A1 and CYP1A2 are simultaneously controlled through bidirectional and common regulatory elements.

Key words: Promoter analysis, Cytochrome P450, Regulation - transcriptional, Regulation - xenobiotic, Ah receptor

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