A major glucocorticoid-inducible P450 in rat liver is not P450 3A1.
A new P450 3A cDNA (RL33) has been cloned from a liver cDNA library of untreated male rat. RL33 is 2032 nucleotides in length and has an open reading frame of 502 amino acid residues. The nucleotide sequence of its 5'-noncoding region is completely identical with that of a genomic clone of P450 3A1 isolated by Burger et al. [Proc. Natl. Acad. Sci. USA 89, 2145-2149 (1992)]. Compared with rat P450 3A1, P450 RL33 showed 98 and 97% identities in the nucleotide and deduced amino acid sequences, respectively, with the deletion of 2 amino acids and substitution of 12 amino acids. These residues were localized around amino acids 107-230. Recently Kirita and Matsubara have isolated the same P450 3A cDNA (cDEX) from dexamethasone (DEX)-treated rat liver [Arch. Biochem. Biophys. 307, 253-258 (1993)]. Northern blot analysis using an oligonucleotide probe specific for P450 RL33/cDEX revealed that P450 RL33/cDEX mRNA was induced strongly by pregnenolone 16 alpha-carbonitrile and DEX and weakly by phenobarbital (PB) and triacetyloleandomycin. We constructed a P450 3A cDNA library by the reverse transcriptase-polymerase chain reaction using common primers to P450 RL33/cDEX, 3A1, and 3A2, and subcloned the cDNAs into pUC119. The expression level of P450 RL33/cDEX mRNA was investigated by identifying each clone with the above oligonucleotide probe. P450 RL33/cDEX mRNA represented over 70% of the total P450 3A mRNA from untreated, PB-, and DEX-treated rat liver. These results indicated that the major DEX-inducible form of P450 3A is P450 RL33/cDEX and not P450 3A1.
Komori
M
M
Department of Veterinary Science, University of Osaka Prefecture.
Oda
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D003907:Dexamethasone / Q000494:pharmacology*; D004790:Enzyme Induction; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics*; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D012194:RNA-Directed DNA Polymerase; D051381:Rats; D017207:Rats, Sprague-Dawley
D007527:Isoenzymes; D003907:Dexamethasone; D003577:Cytochrome P-450 Enzyme System; D012194:RNA-Directed DNA Polymerase