Received for publication August 15, 2006.
Revised November 30, 2006.
Accepted for publication December 1, 2006.

Constitutive and 3-MC-induced Rat ALDH3A1 Expression is Mediated by Multiple Xenobiotic Response Elements

Abstract

The rat class three aldehyde dehydrogenase gene (ALDH3A1) is expressed constitutively or by xenobiotic induction depending on the tissue in which it occurs. While the mechanism that mediates inducible expression has been well characterized, relatively little is known about constitutive regulatory mechanisms. Previous ALDH3A1 promoter analyses have indicated that primary regulatory regions within the ALDH3A1 5' flanking region exert similar effects on both constitutive and inducible ALDH3A1 expression. However, promoter gene analyses that served as the basis of early work were limited by the lack of sufficient 5' flanking region sequence. To gain a more complete picture of how the 5' flanking region regulates both modes of expression, we have subcloned an 8.0kb fragment from the 5' flanking region of the ALDH3A1 gene and subjected it to reporter gene analyses. We found a region located between 4.8 and 7.8 kb upstream of the non-coding first exon that drives strong ALDH3A1 reporter activity. This region contains xenobiotic response element (XRE) consensus sequences that mediate constitutive and inducible ALDH3A1 reporter gene expression. Using the new generation of ALDH3A1 reporter constructs we were unable to confirm the presence of a negative regulatory region that was apparent in previous studies using a shorter fragment of the 5' flanking region. We also demonstrate that 3-methyl cholanthrene induces ALDH3A1 expression above high constitutive background in corneal epithelial cells.

Key words: Ah receptor, ARNT, polycyclic aromatic hydrocarbons, regulation of gene expression