IDENTIFICATION OF CYTOCHROME-P-450 1A (CYP1A) GENES FROM 2 TELEOST FISH, TOADFISH (OPSANUS-TAU) AND SCUP (STENOTOMUS CHRYSOPS), AND PHYLOGENETIC ANALYSIS OF CYP1A GENES

Cytochrome P-450-mediated responses to environmental challenges are we ll known in diverse animal taxa, but the evolution of the complex gene superfamily coding for these enzymes is poorly understood, Here we re port a phylogenetic analysis of the cytochrome P-450 1A (CYP1A) genes including two new sequences determined from teleost fish, toadfish (Op sanus tau) and scup (Stenotomus chrysops). Degenerate PCR primers were used to amplify a 1.2 kbp fragment from liver cDNA. The toadfish PCR product was used as a probe to identify a full-length CYP1A clone from a toadfish liver cDNA library. The entire coding region of the scup C YP1A was obtained by rapid amplification of cDNA ends (RACE) using spe cific primers based on the sequence of the partial PCR product. The pr edicted protein sequences for toadfish and scup CYP1A shared 78% and 8 3% amino acid identity with rainbow trout CYP1A1 respectively. Amino a cid identity with mammalian CYP1A proteins ranged from 51 to 60% for 5 05 aligned positions, Phylogenetic analysis of four teleost fish CYP1A genes (trout, toadfish, scup and plaice) and 12 mammalian CYP1A genes suggests a monophyletic origin of the teleost genes, with the trout g ene being most divergent, and indicates three distinct groupings: mamm alian 1A1, mammalian 1A2, and fish 1A. This supports the idea that the gene duplication event which gave rise to CYP1A1 and CYP1A2 occurred after the divergence of the lines leading to mammals and fish. These r esults establish a molecular phylogeny within the CYP1A subfamily, the first such detailed phylogenetic analysis within a cytochrome P-450 f amily.