Isolation and sequence analysis of the eel cytochrome P450 1A1 gene

The putative CYP1A1 gene was isolated from a genomic library of eel (Anguilla japonica) chromosomal DNA. Sequence analysis of 8184 bp showed that the clone obtained was the structural gene of CYP1A1, which consisted of seven exons and six introns in a region approximately 5800 bp in length, as well as a 5' upstream region of about 2300 bp. The initiation codon was found not in the first exon, but in the second exon, as was reported for the CYP1A genes of mammals and fish. The GC box, CAAT box, and TATA box were located proximately to the first exon, at 110, 62, and 38 bp upstream of the transcriptional start site, respectively. We found six core sequences of xenobiotic-responsive elements (XREs) in the 5' upstream region, and also one in the first intron. AU the XRE core sequences in the 5' upstream region were unique in their localization in the sense strand. The XRE core sequence in the first intron was in the antisense strand.