title: cDNA clones for liver cytochrome P-450s from individual aroclor-treated rats: constitutive expression of a new P-450 gene related to phenobarbital-inducible forms.
abstract: Differential hybridization and screening with cloned inserts was used to identify two families of cytochrome P-450 cDNA clones in libraries prepared from total liver poly(A)+RNA of individual Aroclor-treated rats. One family has cDNA inserts for the major phenobarbital-inducible P-450s, P-450b and P-450e. Two types of P-450e inserts were identified. In addition, irregular inserts were characterized from two clones (PB23 and PB24) of this group. The other family has cDNA inserts for the major 3-methylcholanthrene-inducible species, P-450c and P-450d. No coding sequence restriction site variants were detected among 26 P-450d and P-450c inserts analyzed. The restriction map of the irregular 2.2-kb PB23 insert has a P-450b-like portion, followed by a 3' extension that hybridizes to RNAs of 2.7 and 4.8 kb, which are also detectable with a classical P-450b probe. The PB23 insert and the 2.7- and 4.8-kb RNAs presumably represent 3' extensions of P-450b/P-450e mRNAs, polyadenylated at downstream sites. The 858-bp sequence of the PB24 insert encodes the carboxy-terminal portion of a P-450b/P-450e-like protein. There is approximately 20% divergence at the polypeptide level between the PB24 and P-450b/P-450e sequences; nevertheless, they share many essential features. A PB24-specific probe hybridizes to a 1.9-kb RNA species which is present in the liver of untreated rats and which is not appreciably induced by phenobarbital or Aroclor. The PB24 cDNA most likely represents a constitutive cytochrome P-450, related to phenobarbital-inducible forms.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001140:Aroclors / Q000494:pharmacology*; D001483:Base Sequence; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D004247:DNA / Q000378:metabolism*; D004251:DNA Transposable Elements; D004790:Enzyme Induction; D005796:Genes / Q000187:drug effects*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009693:Nucleic Acid Hybridization; D010634:Phenobarbital / Q000494:pharmacology*; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001140:Aroclors; D004251:DNA Transposable Elements; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D011078:Polychlorinated Biphenyls; D010634:Phenobarbital