Molecular Cloning of cDNA for Guinea Pig CYP1A2 Comparison with Guinea Pig CYP1A1

Guinea pig CYP1A2 cDNA was isolated by RT-PCR from liver tissue of 3,3′-methylcholanthrene-treated guinea pigs. It shares considerable sequence identity with guinea pig CYP1A1 (nt 77%, aa 65%), but differs in levels of constitutive expression, function, and inducibility. Western blot analysis of protein expressed by full-length cDNA in COS-1 cells identified CYP1A2 (56 kDa) and CYP1A1 (53 kDa) proteins in corun liver microsomes. CYP1A2 transfectants metabolized methoxyresorufin and ethoxyresorufin, while CYP1A1 transfectants metabolized only ethoxyresorufin. Constitutive expression of CYP1A2 mRNA (2.0 kb) and protein was much lower than that of CYP1A1 mRNA (2.6 kb) and protein, but the fold induction of CYP1A2 by 3,3′-methylcholanthrene was greater than that of CYP1A1. Changes in splicing of CYP1A2 pre-mRNA occur upon treatment with 3,3′-methylcholanthrene.