Identification of a Rat Adrenal Cytochrome P450 Active in Polycyclic Hydrocarbon Metabolism as Rat CYP1B1

Abstract

Antibodies against a novel adrenocorticotropic hormone-inducible cytochrome P450 (P450RAP), responsible for polycyclic aromatic hydrocarbon metabolism in rat adrenal microsomes (Otto, S., Bhattacharyya, K. K., and Jefcoate, C. R. (1992) Endocrinology 131, 3067–3076), identified a cDNA clone encoding a partial cytochrome P450 sequence from a rat adrenal cDNA library. Rescreening a second cDNA library yielded several clones up to 5.0 kilobases (kb) encoding a 1629-base pair open reading frame. The deduced amino acid sequence (543 residues) matched completely with five peptides cleaved from P450RAP. The amino acid sequence of P450RAP is 92% identical to a 2,3,7,8-tetraehlorodibenzo-p-dioxin-inducible CYP1B1, cloned from mouse C3H10T1/2 (10T1/2) embryo fibroblast cells (Savas, Ü., Bhattacharyya, K. K., Christou, M., Alexander, D. L., and Jefcoate, C. R. (1994) J. Biol. Chem. 269, 14905–14911), which shows nearly the same characteristics in polycyclic aromatic hydrocarbon metabolism. The available 5′- and 3′-noncoding regions show, respectively, 93 and 83% sequence identity. We conclude that P450RAP protein is encoded by a rat CYP1B1 gene orthologous to the mouse CYP1B1 gene. Alignment of rat CYP1B1 amino acid sequences with rat CYP1A1 (39% identical) indicated eight regions of high identity for each (60–78%), interspersed by extensive regions of less than 30% similarity. The CYP1B1 cDNAs hybridize a 5.2-kb mRNA in rat adrenals, consistent with the length of the longest clones and the mRNA recognized in 10T1/2 cells. CYP1B1 mRNA was elevated by a 2-day adrenocorticotropic hormone treatment but much less than CYP11A1 (cytochrome P450 side chain cleavage) mRNA (2-fold versus 4-fold). The lower levels of the 5.2-kb mRNA in other steroidogenic cells (ovary) was consistent with the amount of immunodetectable CYP1B1 protein and, unlike the adrenal, expression in the ovary was stimulated 5-fold by β-naphthoflavone, an aryl hydrocarbon receptor agonist, in parallel with CYP1A1 induction. In several other tissues (liver > lung > uterus ≫ kidney), CYP1B1 mRNA and protein were constitutively undetectable but highly induced by β-naphthoflavone, although at much lower levels than CYP1A1. Rat CYP1B1, therefore, exhibits regulation through hormonal signaling and the aryl hydrocarbon receptor in a cell-specific manner. Antibodies against a novel adrenocorticotropic hormone-inducible cytochrome P450 (P450RAP), responsible for polycyclic aromatic hydrocarbon metabolism in rat adrenal microsomes (Otto, S., Bhattacharyya, K. K., and Jefcoate, C. R. (1992) Endocrinology 131, 3067–3076), identified a cDNA clone encoding a partial cytochrome P450 sequence from a rat adrenal cDNA library. Rescreening a second cDNA library yielded several clones up to 5.0 kilobases (kb) encoding a 1629-base pair open reading frame. The deduced amino acid sequence (543 residues) matched completely with five peptides cleaved from P450RAP. The amino acid sequence of P450RAP is 92% identical to a 2,3,7,8-tetraehlorodibenzo-p-dioxin-inducible CYP1B1, cloned from mouse C3H10T1/2 (10T1/2) embryo fibroblast cells (Savas, Ü., Bhattacharyya, K. K., Christou, M., Alexander, D. L., and Jefcoate, C. R. (1994) J. Biol. Chem. 269, 14905–14911), which shows nearly the same characteristics in polycyclic aromatic hydrocarbon metabolism. The available 5′- and 3′-noncoding regions show, respectively, 93 and 83% sequence identity. We conclude that P450RAP protein is encoded by a rat CYP1B1 gene orthologous to the mouse CYP1B1 gene. Alignment of rat CYP1B1 amino acid sequences with rat CYP1A1 (39% identical) indicated eight regions of high identity for each (60–78%), interspersed by extensive regions of less than 30% similarity. The CYP1B1 cDNAs hybridize a 5.2-kb mRNA in rat adrenals, consistent with the length of the longest clones and the mRNA recognized in 10T1/2 cells. CYP1B1 mRNA was elevated by a 2-day adrenocorticotropic hormone treatment but much less than CYP11A1 (cytochrome P450 side chain cleavage) mRNA (2-fold versus 4-fold). The lower levels of the 5.2-kb mRNA in other steroidogenic cells (ovary) was consistent with the amount of immunodetectable CYP1B1 protein and, unlike the adrenal, expression in the ovary was stimulated 5-fold by β-naphthoflavone, an aryl hydrocarbon receptor agonist, in parallel with CYP1A1 induction. In several other tissues (liver > lung > uterus ≫ kidney), CYP1B1 mRNA and protein were constitutively undetectable but highly induced by β-naphthoflavone, although at much lower levels than CYP1A1. Rat CYP1B1, therefore, exhibits regulation through hormonal signaling and the aryl hydrocarbon receptor in a cell-specific manner. The toxicity and carcinogenicity of polycyclic aromatic hydrocarbons (PAH) 1The abbreviations used are: PAH, polycyclic aromatic hydrocarbon; CYP1A1, cytochrome P4501A1: AhR, aryl hydrocarbon receptor; 10T172, C3H10T1/2 mouse embryo fibroblasts; P450EF, mouse embryo fibroblast cytochrome P450; kb, kilobase(s); bp, base pair(s); mCYP1B1, mouse cytochrome P4501B1; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin; SCC, squamous cell carcinoma; hCYP1B1, human cytochrome P4501B1; P450RAP, rat adrenal cytochrome P450 protein; DMBA, 7,12-dimethylbenz[a]anthracene; rCYP1B1, rat cytochrome P4501B1; ACTH, adrenocorticotropic hormone; β-NF, β-naphthoflavone; HPLC, high performance liquid chromatography; PCR, polymerase chain reaction. is dependent for the most part on metabolism to dihydrodiol epoxides, which are particularly reactive with DNA (1Pelkonen O. Nebert D.W. Pharmacol. Rev. 1982; 34: 189-222PubMed Google Scholar, 2Sims P. Grover P.L. Gelboin H.V. Tso P.O.P. Polycyclic Hydrocarbons and Cancer. Vol. 3. Academic Press, Inc., New York1981: 117-181Google Scholar). This activity is stimulated in many cell types following exposure to PAH through increased synthesis of cytochrome P4501A1 (CYP1A1), which is particularly effective in PAH metabolism (3Wilson N.M. Christou M. Turner C.R. Wrighton S.A. Jefcoate C.R. Carcinogenesis. 1984; 5: 1475-1483Crossref PubMed Scopus (94) Google Scholar). This stimulation is brought about in diverse species through increased gene transcription mediated by binding of the PAH to the aryl hydrocarbon receptor (AhR) (4Shen E.S. Whitlock Jr., J.P. J. Biol. Chem. 1992; 267: 6815-6819Abstract Full Text PDF PubMed Google Scholar, 5Lusska A. Shen E. Whitlock Jr., J.P. J. Biol. Chem. 1993; 268: 6575-6580Abstract Full Text PDF PubMed Google Scholar). This ligand activated helix-loop-helix protein (6Burbach K.M. Poland A. Bradfield C.A. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: 8185-8189Crossref PubMed Scopus (723) Google Scholar) forms a complex with the related AhR nuclear translocator protein in the nucleus (7Reyes H. Reisz-Porszasz S. Hankinson O. Science. 1992; 256: 1193-1195Crossref PubMed Scopus (689) Google Scholar, 8Probst M.R. Reisz-Porszasz S. Agbunag R.V. Ong M.S. Hankinson O. Mol. Pharmacol. 1993; 44: 511-518PubMed Google Scholar), and the heterodimer recognizes specific DNA enhancer sequences, including those in the 5′ upstream region of the CYP1A1 gene (9Whitlock Jr., J.P. Chem. Res. Toxicol. 1993; 6: 754-763Crossref PubMed Scopus (359) Google Scholar, 10Fujii-Kuriyama Y. Imataka H. Sogawa K. Yasumoto K.I. Kikuchi Y. FASEB J. 1992; 6: 706-710Crossref PubMed Scopus (107) Google Scholar). We have characterized a second related cytochrome P450 that is the dominant form in C3H10T1/2 (10T1/2) mouse embryo fibroblasts (P450EF) and is very active in PAH metabolism (11Pottenger L.H. Christou M. Jefcoate C.R. Arch. Biochem. Biophys. 1991; 286: 488-497Crossref PubMed Scopus (71) Google Scholar). This protein is induced by PAH in rodent fibroblasts from a variety of sources including fetal tissue, uterus, prostate, and breast (11Pottenger L.H. Christou M. Jefcoate C.R. Arch. Biochem. Biophys. 1991; 286: 488-497Crossref PubMed Scopus (71) Google Scholar, 12Savas U. Christou M. Jefcoate C.R. Carcinogenesis. 1993; 14: 2013-2018Crossref PubMed Scopus (36) Google Scholar). A cDNA that probably encodes P450EF has been cloned from 10T1/2 cells (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar). This cDNA encodes a translated sequence that is 41% identical to mouse CYP1A1 and a very large 3′-untranslated region consistent with a 5.2-kilobase (kb) mRNA, which is uniquely hybridized by this cDNA. This mRNA shows the same pattern of induction and tissue distribution as the 55-kDa protein, recognized by antibodies raised against P450EF purified from 10T1/2 cells. Based on the sequence identity to CYP1A1, this new form has been designated as mouse CYP1B1 (mCYP1B1), and based on the expression characteristics, identity with the purified 10T1/2 form has been assumed but not proved. A cDNA corresponding to a 5.2-kb mRNA that is induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has also been cloned from a human squamous cell carcinoma (SCC) cell line based on differential expression (14Sutter T.R. Tang Y.M. Hayes C.L. Wo Y.P. Jabs E.W. Li X. Yin H. Cody C.W. Greenlee W.F. J. Biol Chem. 1994; 269: 13092-13099Abstract Full Text PDF PubMed Google Scholar). This human cDNA sequence, which is 80% identical to the mouse sequence and retains the full characteristics of a P450 cytochrome, has been identified as the human CYP1B1 (hCYP1B1). A 52-kDa TCDD-inducible protein has been recognized with antibodies raised against purified P450EF and a rat adrenal cytochrome P450 (P450RAP) in human SCC and mammary carcinoma cell lines and is induced by TCDD in each cell type (15Christou M. Savas U. Spink D.C. Gierthy J.F. Jefcoate C.R. Carcinogenesis. 1994; 15: 725-732Crossref PubMed Scopus (82) Google Scholar). These antibodies inhibit PAH metabolism in these mammary cells, which also shows a product selectivity consistent with the hCYP1B1. While cDNA sequence and mRNA expression data is now available for two members of this new cytochrome P450 subfamily, no direct protein data have been provided to establish that the CYP1B1 sequence actually encodes either the immu-nodetectable proteins or the cytochrome P450 responsible for PAH metabolism. We have recently purified and characterized a P450RAP that is immunologically closely related to P450EF (16Otto S. Marcus C. Pidgeon C. Jefcoate C. Endocrinology. 1991; 129: 970-982Crossref PubMed Scopus (110) Google Scholar, 17Otto S. Bhattacharyya K.K. Jefcoate C.R. Endocrinology. 1992; 131: 3067-3076Crossref PubMed Scopus (110) Google Scholar). This protein catalyzes PAH metabolism with a product distribution similar to that produced by the putative CYP1B1 of 10T1/2 cells. This distribution for 7,12-dimethylbenz[a]anthracene (DMBA) is completely different from that catalyzed by CYP1A1. Unlike the related mouse cytochrome P450EF, P450RAP is to hormonal stimulation of rat but is by AhR In this the of a which exhibits a high to mCYP1B1, from a cDNA library from rat We amino acid sequences for five peptides from purified rat adrenal P450RAP and that these are identical to sequences encoded by rat adrenal CYP1B1 the identity of P450RAP with We that is P450 in either hormonal regulation or stimulation by AhR in a highly manner. were used in including and were from for of P450RAP were from were with adrenocorticotropic hormone or for were as to or were with or the induction were with in for either for protein or for were by for and following the for the tissues were and used for or liquid microsomes were from rat adrenals, as (16Otto S. Marcus C. Pidgeon C. Jefcoate C. Endocrinology. 1991; 129: 970-982Crossref PubMed Scopus (110) Google Scholar), were and an with and The was with the and with the same The were was by with in and a The was and with a of in The P450RAP were by as and against and a and with a of in The P450RAP a and several The P450RAP from was by and the P450RAP protein either to a and with for sequence P. J. Biol. Chem. Full Text PDF PubMed Google Scholar) or to a with and with for sequence J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, H. P. A to and for Academic Press, Inc., New Scholar). were to acid and a with in acid to peptides were as a of in acid at a of and the protein were at the of and protein to from the J. Biol. Chem. 256: Full Text PDF PubMed Google Scholar). were and by two and with the data from the same by an data The provided of identified for were for and to of by the for each in the of was from rat by the PubMed Scopus Google Scholar) and was J. A Scholar). A cDNA library was in with a by following the A second cDNA library was in with a of and a P450RAP mRNA to J. A Scholar). The P450RAP was based on the of a P450RAP cDNA from library A. The cDNA were to the J. A Scholar). cDNA library A was with a raised against purified P450RAP (16Otto S. Marcus C. Pidgeon C. Jefcoate C. Endocrinology. 1991; 129: 970-982Crossref PubMed Scopus (110) Google Scholar). an of clones were in the of These clones were purified in of at lower and in five clones the were to to the These and other clones by encoded the of a sequence 80% identical to A to encoding the of the a library was from rat adrenal mRNA and with a from the of cDNA (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar). the J. A Scholar), were and clones were of The clones were to to the from each clone were and to DNA and R. R. 1993; 14: Google Scholar) with a of the by to the DNA The and of these with to P450RAP, were by with the cDNA These were and the were to and to DNA sequence in to S. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar) a U. S. DNA The DNA sequence was and and the deduced amino acid sequence was the The of this was used to P450RAP with mCYP1B1, hCYP1B1, and of from adrenal tissue was on a and for to a by J. A Scholar). The was to the a on and were in the same J. A Scholar). The used for was a of P450RAP and was with a and were at for and were at for in and and to at for several of in of were with of and at for The were at and brought to a of in a of of of and of The were at for and the was by at for The were to that C.A. P. Res. Google Scholar), with a The sequences for of were to a region of CYP1B1 and The sequences used for of were to those C.A. P. Res. Google Scholar). for were from and to the region and of of cDNA from each was used for each in a of with a of of each of DNA polymerase and each and for CYP1B1, or CYP1A1 of on of each the were to the following CYP1B1, the were to and through a at a at and a at following the were from the and of and of DNA polymerase were to each with the to and the same CYP1A1, the were to and through a at a at and a at were through and by to J. A Scholar). The cDNA was by a on and hybridized at for with cDNA for CYP1B1, CYP1A1, and were as and to proteins from different tissues were on and to a proteins were by the as the (16Otto S. Marcus C. Pidgeon C. Jefcoate C. Endocrinology. 1991; 129: 970-982Crossref PubMed Scopus (110) Google Scholar). were by S. Bhattacharyya K.K. Jefcoate C.R. Endocrinology. 1992; 131: 3067-3076Crossref PubMed Scopus (110) Google Scholar). antibodies raised against purified P450RAP from rat adrenal microsomes (16Otto S. Marcus C. Pidgeon C. Jefcoate C. Endocrinology. 1991; 129: 970-982Crossref PubMed Scopus (110) Google Scholar) were used to a cDNA expression library from the mRNA of rat A clone was identified and This clone was and to the amino of a P450 cytochrome and to the a 3′-untranslated Rescreening of this library with provided related cDNA but of which the part of the cytochrome library was with against of the of respectively, or a of to the A of cDNA (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar) was used to cDNA clones for in library The clones from library of types based on and clones from library A a type The each was about type clones from library A type clones a of than and each about to the of the 5.2-kb The sequences and the of clones were that from a of type the full of the 3′-untranslated the and about of the A is for sequences and the recently hCYP1B1. These sequences to a high of identity in the 5′- and 3′-noncoding regions as and The translated sequence of the region of the rat cytochrome P450 is in The sequence is 92% identical to recently cloned by of (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar) and probably the rat acid of rat CYP1B1 with mouse CYP1B1, human CYP1B1, and rat CYP1A1. The P450RAP amino acid sequence was used to the with mouse CYP1B1 (mCYP1B1), human CYP1B1 and rat CYP1A1 the of the shows the regions the amino acid of and human CYP1B1 are shows the regions the amino acid of are identical to line the of the In to establish that encodes the P450RAP protein, purified protein to with a that The by HPLC, provided peptides that were and These sequences, with the sequence, are in The to of the cDNA is in the of the sequence and are by a is to the that the sequence of each is identical to an amino acid sequence from were in most with corresponding sequences in mCYP1B1, in for were of amino This that encodes the protein and sequences of P450 in a new The cDNAs and types each hybridize a 5.2-kb mRNA in rat adrenal tissues A 2-day stimulation produced a in 5.2-kb mRNA to in which is highly the other CYP11A1 (cytochrome P450 side chain cleavage) mRNA, which is to by and M.R. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar), a in the same A similar to stimulation was in a of and treatment of and CYP11A1 mRNA a that the by in to a direct A at (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar, J. Proc. Natl. Acad. Sci. 1993; PubMed Scopus Google Scholar) in mouse fibroblasts was A 5.2-kb mRNA species was also with these cDNAs at lower levels in other steroidogenic and not was from several tissues from either or following a treatment with β-NF, an to through the In direct with mRNA from these was 5.2-kb mRNA was and to not transcription with specific was for of A P450RAP cDNA the region was used to hybridize the and uterus not with the with A was for lung that was increased by was in the by the lung and was in the The levels in the steroidogenic ovary were elevated by β-NF, a was for the adrenal, the levels are transcription of mRNA was also on the same although with much less uterus and the was of these were than for the and In the adrenal, expression of was induction. Based on the of these on the are to the levels of in the ovary are to this This also levels of mRNA to in and Rat microsomes from tissues with and induction have been with antibodies raised against P450RAP and The expression of a closely the expression of the was induction in and uterus and was at a much lower than expression and The induced expression of the by was in and uterus, than in and induced expression was in uterus and was no in this in adrenal which was at a than in the levels were to about S. Bhattacharyya K.K. Jefcoate C.R. Endocrinology. 1992; 131: 3067-3076Crossref PubMed Scopus (110) Google of CYP1B1 and CYP1A1 protein in rat tissue in a new cDNAs corresponding to the respectively, the mouse and human CYP1B1 have recently been cloned (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar, T.R. Tang Y.M. Hayes C.L. Wo Y.P. Jabs E.W. Li X. Yin H. Cody C.W. Greenlee W.F. J. Biol Chem. 1994; 269: 13092-13099Abstract Full Text PDF PubMed Google Scholar). This the sequence a of the CYP1B1 gene and a purified and active cytochrome Rat adrenal CYP1B1, sequence is has sequence identity to five peptides amino from purified adrenal P450RAP, which has been characterized as and active in the metabolism of PAH (16Otto S. Marcus C. Pidgeon C. Jefcoate C. Endocrinology. 1991; 129: 970-982Crossref PubMed Scopus (110) Google Scholar). Rat adrenal CYP1B1 exhibits 92% amino acid identity to mouse embryo fibroblast The are to that also from human CYP1B1, which was recently cloned from a SCC cell line (14Sutter T.R. Tang Y.M. Hayes C.L. Wo Y.P. Jabs E.W. Li X. Yin H. Cody C.W. Greenlee W.F. J. Biol Chem. 1994; 269: 13092-13099Abstract Full Text PDF PubMed Google Scholar) and which 80% identity to this rat CYP1B1 The are consistent with these sequences encoding and human for a CYP1B1 gene. We have two types of regulation for rat hormonal regulation in steroidogenic tissues as the adrenal and (16Otto S. Marcus C. Pidgeon C. Jefcoate C. Endocrinology. 1991; 129: 970-982Crossref PubMed Scopus (110) Google Scholar, 17Otto S. Bhattacharyya K.K. Jefcoate C.R. Endocrinology. 1992; 131: 3067-3076Crossref PubMed Scopus (110) Google Scholar), is also and AhR which is in and expression is While P450RAP in rat ovary is induced by human S. Bhattacharyya K.K. Jefcoate C.R. Endocrinology. 1992; 131: 3067-3076Crossref PubMed Scopus (110) Google Scholar), that is also induction through the We also expression in the uterus, the regulation is and induction by expression of CYP1B1 in and to the adrenal, the of steroidogenic cells in the tissues A. J. Chem. Biol. PubMed Scopus Google Scholar, M. J. PubMed Scopus Google Scholar). The high induction by in the ovary to the adrenal from in other cell types than the steroidogenic cells the or the The expression in the uterus the expression of CYP1B1 in fibroblasts U. Christou M. Jefcoate C.R. Carcinogenesis. 1993; 14: 2013-2018Crossref PubMed Scopus (36) Google Scholar) that has been identified in cell While most tissues levels of the related form CYP1A1, the induction of CYP1B1 was nearly in the This is consistent with a high of expression in which have to CYP1B1 but not CYP1A1 of the AhR (11Pottenger L.H. Christou M. Jefcoate C.R. Arch. Biochem. Biophys. 1991; 286: 488-497Crossref PubMed Scopus (71) Google Scholar, 12Savas U. Christou M. Jefcoate C.R. Carcinogenesis. 1993; 14: 2013-2018Crossref PubMed Scopus (36) Google Scholar). The expression of CYP1A1 was lower in steroidogenic cells of the adrenal, and The of expression in and also from the fibroblast have that rat fibroblasts rat this same for Alexander and C. R. Jefcoate, The cDNAs hybridized an large 5.2-kb mRNA in the rat This is identical to the mRNA species recognized by CYP1B1 in mouse and human tissues to (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar, T.R. Tang Y.M. Hayes C.L. Wo Y.P. Jabs E.W. Li X. Yin H. Cody C.W. Greenlee W.F. J. Biol Chem. 1994; 269: 13092-13099Abstract Full Text PDF PubMed Google Scholar). The of this mRNA also closely to the of the longest cDNA cloned from the rat adrenal A library. shows as for the mouse and human a region for amino is by a sequence and of 3′-untranslated sequence, which a sequence at the (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar). A high of sequence identity is rat and human in these regions of the CYP1B1 mRNA, that for these sequences are of the clones from library A in the same region of the sequence the of in CYP1B1 mRNA by This is by the of this for a library from the same mRNA to hormonal regulation and induction in these expression of 5.2-kb mRNA and protein the these In have the amino acid sequences of the CYP1B1 and regions with the sequence of the in the active are to each PAH as and at specific The of these different as by in for DMBA, CYP1B1 and CYP1A1 and (11Pottenger L.H. Christou M. Jefcoate C.R. Arch. Biochem. Biophys. 1991; 286: 488-497Crossref PubMed Scopus (71) Google Scholar, S. Marcus C. Pidgeon C. Jefcoate C. Endocrinology. 1991; 129: 970-982Crossref PubMed Scopus (110) Google Scholar). shows a high of identity with (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar) and (14Sutter T.R. Tang Y.M. Hayes C.L. Wo Y.P. Jabs E.W. Li X. Yin H. Cody C.W. Greenlee W.F. J. Biol Chem. 1994; 269: 13092-13099Abstract Full Text PDF PubMed Google Scholar). The sequence identity of and with is in the amino The amino of and are completely The most sequence actually to of the peptides from P450RAP, to the identity the and cDNA These sequence that P450EF protein from 10T1/2 cells is encoded by This has been recently by that exhibits metabolism. Savas and C. R. Jefcoate, While the of amino acid identity of with is sequences of amino identity by in A of identity is also corresponding to part of the PubMed Scopus Google Scholar). These sequences are interspersed by regions of of these sequences to identified based on the of cytochrome and cytochrome from J. J. Biol. Chem. Full Text PDF PubMed Google Scholar, C.A. J. Science. 1993; PubMed Scopus Google Scholar). is a in P450 that is for protein S. K. K. M. K. J. Biochem. 1993; PubMed Scopus Google Scholar). A has been for CYP1A1 as most of A and based on a with of cytochrome PubMed Scopus Google Scholar). This in a of that has been in binding (13Savas U. Bhattacharyya K.K. Christou M. Alexander D.L. Jefcoate C.R. J. Biol. Chem. 1994; 269: 14905-14911Abstract Full Text PDF PubMed Google Scholar, K. O. K. Y. J. Biol Chem. Full Text PDF PubMed Google Scholar). the part of the This the that is to the is the sequence that the amino amino and amino have no with in other is for a of to a of amino These regions of high CYP1B1 and CYP1A1 in in these particularly no parallel is in other The regulation and cell of expression of a The to the AhR in tissues but not also to the of this The high sequence is consistent with in which is also indicated by the of for CYP1B1 proteins the PAH of a a We Savas for of the sequence We also and for in for and for in the We also for of the