Cloning of CYP1A in Atlantic salmon (Salmo salar)

To better understand the molecular relationship between contaminant exposure in Atlantic salmon and the cytochrome P450 system, we have cloned a CYP1A gene using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The cloned cDNA possesses all characteristic motifs of teleost CYP1A genes including the start codon, heme-binding region, stop codon, and poly-adenylation signal. The cloned gene is also characterized by an extended 3′ untranslated region (UTR; 1025bp) containing three AUUUA sequences that are likely to be a target for rapid degradation of its mRNA. Its coding region (1569 base pairs) shares 97.4% and 96.7% sequence identity with the corresponding regions of rainbow trout CYP1A1 and CYP1A3 genes, respectively. In addition, the deduced amino acid sequence of salmon CYP1A shows 96.9% and 96.2% identity with rainbow trout P450 1A1 and P450 1A3 enzymes, respectively. Phylogenetic analysis of a sample of CYP genes confirmed that Atlantic salmon CYP1A is closely related to rainbow trout CYP1A genes as well. Northern analysis showed that CYP1A mRNA is at a significantly higher level in the liver of Atlantic salmon injected intraperitoneally with β-Naphthoflavone (BNF), suggesting that this gene is inducible. Southern analysis verified the presence of at least one copy of the CYP1A gene in the genomic DNA of Atlantic salmon. These results reveal the transcriptional and inductive properties of an Atlantic salmon CYP1A gene with an extended 3′ UTR, and provide molecular tools for studying the effects of xenobiotics on Atlantic salmon populations.