Human ADA3 Binds to Estrogen Receptor (ER) and Functions As a Coactivator for ER-mediated Transactivation

Abstract

We have recently identified the hADA3 protein, the human homologue of yeast transcriptional coactivator yADA3, as a novel HPV16 E6 target. Using ectopic expression approaches, we further demonstrated that hADA3 directly binds to the 9-cis retinoic acid receptors α and β, and functions as a coactivator for retinoid receptor-mediated transcriptional activation. Here, we examined the role of endogenous hADA3 as a coactivator for estrogen receptor (ER), an important member of the nuclear hormone receptor superfamily. We show that ADA3 directly interacts with ERα and ERβ. Using the chromatin immunoprecipitation assay, we also show that hADA3 is a component of the activator complexes bound to the native ER response element within the promoter of the estrogen-responsive gene pS2. Furthermore, using an ER response element-luciferase reporter, we show that overexpression of ADA3 enhances the ERα- and ERβ-mediated sequence-specific transactivation. Reverse transcription-PCR analysis showed an ADA3-mediated increase in estrogen-induced expression of the endogenous pS2 gene. More importantly, using RNA interference against hADA3, we demonstrate that inhibition of endogenous hADA3 inhibited ER-mediated transactivation and the estrogen-induced increase in the expression of pS2, cathepsin D, and progesterone receptor, three widely known ER-responsive genes. The HPV E6 protein, by targeting hADA3 for degradation, inhibited the ERα-mediated transactivation and the protein expression of ER target genes. Thus, our results demonstrate that ADA3 directly binds to human estrogen receptor and enhances the transcription of ER-responsive genes, suggesting a broader role of mammalian hADA3 as a coactivator of nuclear hormone receptors and the potential role of these pathways in HPV oncogenesis. We have recently identified the hADA3 protein, the human homologue of yeast transcriptional coactivator yADA3, as a novel HPV16 E6 target. Using ectopic expression approaches, we further demonstrated that hADA3 directly binds to the 9-cis retinoic acid receptors α and β, and functions as a coactivator for retinoid receptor-mediated transcriptional activation. Here, we examined the role of endogenous hADA3 as a coactivator for estrogen receptor (ER), an important member of the nuclear hormone receptor superfamily. We show that ADA3 directly interacts with ERα and ERβ. Using the chromatin immunoprecipitation assay, we also show that hADA3 is a component of the activator complexes bound to the native ER response element within the promoter of the estrogen-responsive gene pS2. Furthermore, using an ER response element-luciferase reporter, we show that overexpression of ADA3 enhances the ERα- and ERβ-mediated sequence-specific transactivation. Reverse transcription-PCR analysis showed an ADA3-mediated increase in estrogen-induced expression of the endogenous pS2 gene. More importantly, using RNA interference against hADA3, we demonstrate that inhibition of endogenous hADA3 inhibited ER-mediated transactivation and the estrogen-induced increase in the expression of pS2, cathepsin D, and progesterone receptor, three widely known ER-responsive genes. The HPV E6 protein, by targeting hADA3 for degradation, inhibited the ERα-mediated transactivation and the protein expression of ER target genes. Thus, our results demonstrate that ADA3 directly binds to human estrogen receptor and enhances the transcription of ER-responsive genes, suggesting a broader role of mammalian hADA3 as a coactivator of nuclear hormone receptors and the potential role of these pathways in HPV oncogenesis. The nuclear hormone receptors (NRs) 1The abbreviations used are: NR, nuclear hormone receptor; ER, estrogen receptor; PR, progesterone receptor; RXR, 9-cis retinoic acid receptor; RAR, retinoic acid receptor; CBP, cAMP response element-binding protein binding protein; HAT, histone acetyltransferase; ADA, alteration/deficiency in activation; GCN, general control non-repressed; RNAi, RNA interference; GST, glutathione S-transferase; SV40, simian virus 40; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; RT, reverse transcription; ChIP, chromatin immunoprecipitation; E2, 17β-estradiol. are a family of structurally related, ligand-induced transcriptional activators that function as critical regulators of diverse physiological processes, including growth, differentiation, development, and reproduction (1Greschik H. Moras D. Curr. Top. Med. Chem. 2003; 3: 1573-1599Crossref PubMed Scopus (58) Google Scholar, 2Edwards D.P. J. Mammary Gland Biol. Neoplasia. 2000; 5: 307-324Crossref PubMed Scopus (118) Google Scholar). Various NRs control the transcription of distinct subsets of genes in the chromatin environment of the nucleus (3Jacobs M.N. Dickins M. Lewis D.F. J. Steroid. Biochem. Mol. Biol. 2003; 84: 117-132Crossref PubMed Scopus (60) Google Scholar, 4Barnes C.J. Vadlamudi R.K. Kumar R. Cell. Mol. Life. Sci. 2004; 61: 281-291Crossref PubMed Scopus (43) Google Scholar). In general, NRs share a conserved structural and functional organization, with DNA-binding, ligand binding, and transcriptional activation domains (3Jacobs M.N. Dickins M. Lewis D.F. J. Steroid. Biochem. Mol. Biol. 2003; 84: 117-132Crossref PubMed Scopus (60) Google Scholar, 4Barnes C.J. Vadlamudi R.K. Kumar R. Cell. Mol. Life. Sci. 2004; 61: 281-291Crossref PubMed Scopus (43) Google Scholar). Depending on their DNA binding and dimerization properties, NRs are subdivided into two classes: class I NRs function as homodimers and include the steroid hormone receptors, such as the estrogen (ER), androgen, and progesterone (PR) receptors, and class II NRs function as heterodimers with the 9-cis retinoic acid receptor (RXR) and include the receptors for retinoic acid (RAR), vitamin D, thyroid hormone, and peroxisome proliferators (1Greschik H. Moras D. Curr. Top. Med. Chem. 2003; 3: 1573-1599Crossref PubMed Scopus (58) Google Scholar, 2Edwards D.P. J. Mammary Gland Biol. Neoplasia. 2000; 5: 307-324Crossref PubMed Scopus (118) Google Scholar). Binding of cognate ligands induces a conformational change in the ligand-binding domain of NRs, which influences their function with respect to subcellular localization, dimerization, cofactor binding, and transcriptional activity (5Kumar R. Thompson E.B. Steroids. 1999; 64: 310-319Crossref PubMed Scopus (316) Google Scholar). Recent studies have shown that a wide range of NR cofactors perform distinct functions at target promoters, including chromatin modification and remodeling and recruitment of the RNA polymerase II holoenzyme (6Chiba N. Suldan Z. Freedman L.P. Parvin J.D. J. Biol. Chem. 2000; 275: 10719-10722Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar). A number of cofactors have been shown to bind the ligand-binding domains directly via short amphipathic α-helices containing the LXXLL sequence (7He B. Wilson E.M. Mol. Cell. Biol. 2003; 23: 2135-2150Crossref PubMed Scopus (88) Google Scholar, 8Savkur R.S. Burris T.P. J. Pept. Res. 2004; 63: 207-212Crossref PubMed Scopus (211) Google Scholar). Structural studies have demonstrated that a hydrophobic channel (AF2) is exposed on the surface of the ligand-binding domain because of ligand binding, promoting dimerization or interaction with coactivators (4Barnes C.J. Vadlamudi R.K. Kumar R. Cell. Mol. Life. Sci. 2004; 61: 281-291Crossref PubMed Scopus (43) Google Scholar, 5Kumar R. Thompson E.B. Steroids. 1999; 64: 310-319Crossref PubMed Scopus (316) Google Scholar, 6Chiba N. Suldan Z. Freedman L.P. Parvin J.D. J. Biol. Chem. 2000; 275: 10719-10722Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar, 7He B. Wilson E.M. Mol. Cell. Biol. 2003; 23: 2135-2150Crossref PubMed Scopus (88) Google Scholar, 8Savkur R.S. Burris T.P. J. Pept. Res. 2004; 63: 207-212Crossref PubMed Scopus (211) Google Scholar, 9McInerney E.M. Rose D.W. Flynn S.E. Westin S. Mullen T.M. Krones A. Inostroza J. Torchia J. Nolte R.T. Assa-Munt N. Milburn M.V. Glass C.K. Rosenfeld M.G. Genes Dev. 1998; 12: 3357-3368Crossref PubMed Scopus (529) Google Scholar). Two groups of NR coactivators have been widely studied: 1) the p300 and the highly related cAMP response element-binding protein-binding protein (CBP); and 2) the mammalian mediator complexes (TRAP, DRIP, ARC, CRSP, SMCC, etc.) (6Chiba N. Suldan Z. Freedman L.P. Parvin J.D. J. Biol. Chem. 2000; 275: 10719-10722Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar, 10Wallberg A.E. Yamamura S. Malik S. Spiegelman B.M. Roeder R.G. Mol. Cell. 2003; 12: 1137-1149Abstract Full Text Full Text PDF PubMed Scopus (207) Google Scholar, 11Wang G. Cantin G.T. Stevens J.L Berk A.J. Mol. Cell. Biol. 2001; 21: 4604-4613Crossref PubMed Scopus (53) Google Scholar, 12Dotson M.R. Yuan C.X. Roeder R.G. Myers L.C. Gustafsson C.M. Jiang Y.W. Li Y. Kornberg R.D. Asturias F.J. Proc. Natl. Acad. Sci. U. S. A. 2000; 97: 14307-14310Crossref PubMed Scopus (154) Google Scholar). The p300 and CBP proteins are recruited to ligand-activated, DNA-bound NRs by the steroid receptor coactivators (SRC-1, -2, and -3) family of bridging factors (6Chiba N. Suldan Z. Freedman L.P. Parvin J.D. J. Biol. Chem. 2000; 275: 10719-10722Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar, 11Wang G. Cantin G.T. Stevens J.L Berk A.J. Mol. Cell. Biol. 2001; 21: 4604-4613Crossref PubMed Scopus (53) Google Scholar). The steroid receptor coactivator proteins have receptor interaction domains containing LXXLL motifs that contact the ligand-binding domains (13Rachez C. Gamble M. Chang C.P. Atkins G.B. Lazar M.A. Freedman L.P. Mol. Cell. Biol. 2000; 20: 2718-2726Crossref PubMed Scopus (184) Google Scholar). The p300 and CBP proteins are histone acetyltransferases (HATs) that mediate the acetylation of nucleosomal histones, a covalent modification generally associated with the enhancement of transcription (reviewed in references 14An W. Roeder R.G. J. Biol. Chem. 2003; 278: 1504-1510Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar, 15Yuan L.W. Giordano A. Oncogene. 21: PubMed Scopus Google Scholar). studies in yeast have demonstrated coactivator the in The of include the proteins ADA3 and and a histone control R. M.G. W. S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). is that hADA3 as a component of a yeast that and that the functional of the are conserved M. A. R. Genes Dev. 1998; 12: PubMed Scopus Google Scholar). of mammalian and receptor in the yeast have shown a for the of yeast including the gene for transcriptional activation M. A. R. Genes Dev. 1998; 12: PubMed Scopus Google Scholar, A.E. Gustafsson Mol. Cell. Biol. 1999; PubMed Scopus (60) Google Scholar). a functional role of hADA3 in NR transactivation in mammalian known our M. Kumar A. G. G. D. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Using the yeast interaction we recently identified the hADA3 protein as a novel human virus protein A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar). We have demonstrated that the hADA3 protein binds to the to the HPV E6 proteins and to the the HPV16 E6 a role for interaction in In of the yeast for a potential role of hADA3 as a NR of hADA3 as an protein the that E6 the mammalian nuclear hormone receptor function by targeting by using ectopic gene expression approaches, we demonstrated that hADA3 with and functions as a coactivator for human transactivation and that E6 inhibited coactivator function by targeting hADA3 for M. Kumar A. G. G. D. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). We to that a that which acid sequence with hADA3, with human ER A. C. R. Res. PubMed Scopus Google suggesting the that hADA3 the of we have examined the of human as as ADA3 proteins with to by A. C. R. Res. PubMed Scopus Google we demonstrate that human and ADA3 directly with ERα and the ERα-mediated transactivation of ER-responsive is that in the of the endogenous hADA3 protein to an inhibition of the expression of ER-responsive genes. Thus, hADA3 protein functions as a critical component of a mammalian coactivator for the estrogen receptor, the that a role as a coactivator for of the hADA3 hADA3 and E6 been A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar). A ADA3 expression the sequence of into for expression and in to A expression in The by three of an to that in the ER-responsive in The the by M. and a and and in with in with the of hADA3 been M. Kumar A. G. G. D. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar). against progesterone receptor, and against cathepsin In Binding proteins and in and hADA3 or in ERα and in and in using a in in the of of proteins with of GST, A and or in or bound to in of and for in the or of or in the of at The with and bound proteins by and by The expression of proteins using the In of hADA3 or and in for The with of and of hADA3 or using the of the with of or in the in the binding and and of protein with for at The with the binding and the bound proteins by in the by and with to The with to the expression of to pS2 ADA3 and as R. Biol. PubMed Scopus Google Scholar). In with to the proteins to The and in and and to to of chromatin to with or DNA associated with the and used for of a containing the in pS2 promoter and or and in for The with and expression in using the also of to the in The of DNA by the of the or with or of for an The and the for using a RNA and for pS2 or in for by or with or for an The RNA using the of RNA used for and used to the pS2 sequence reverse by using reverse used as an control for the RNA and for in for by of control or hADA3 and using to the the with or of for RNA and with of RNA using pS2 as reverse reverse and hADA3 and reverse The and as of the hADA3 E.M. J. A. M. M. W. B. R. W. G. R. 2004; PubMed Scopus Google used for RNA expression in mammalian The used to an DNA for hADA3 RNA to in the hADA3 and a DNA for in the by the expression with the into using the M. J. Res. Google Scholar). of and as Mol. Biol. 2003; Google Scholar). in for and the expression of endogenous hADA3 in nuclear using the as Mol. Biol. 2003; Google Scholar). of ER in or in for by with or of for in containing and and of protein to with and hADA3 and with ERα and have shown a for yeast ADA3 for transcriptional activation by human and NRs these in yeast M. A. R. Genes Dev. 1998; 12: PubMed Scopus Google Scholar, A.E. Gustafsson Mol. Cell. Biol. 1999; PubMed Scopus (60) Google Scholar). Furthermore, we have recently shown that hADA3 binds to and functions as a coactivator for M. Kumar A. G. G. D. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the homologue of which a with hADA3, to bind to human ER A. C. R. Res. PubMed Scopus Google suggesting a coactivator function of to the interaction of and human ADA3 with a we examined the binding of or to in using M. Kumar A. G. G. D. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar, A. C. R. Res. PubMed Scopus Google Scholar). as a showed binding to hADA3 showed binding and is that and bound to and binding in the as the of the ligand and In of the with an the hADA3 or binding to ERα and results demonstrate that hADA3 and bind directly to ER in a to our results with binding M. Kumar A. G. G. D. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). A. C. R. Res. PubMed Scopus Google used a reverse binding assay, with in and we also further binding using a the binding in for the of to hADA3 and bind to ERα in a and of ER binding to hADA3 demonstrated by binding to the of hADA3 to the and by domain analysis of ERα and bind to is to binding to hADA3 also binds to these results demonstrate a binding of ER to and human ADA3 and show that the domain in the of the ERα with hADA3 and in of the in binding we used of proteins to hADA3 and with ERα in mammalian we hADA3 or with ERα in hADA3 on and the of associated using A of hADA3 as as with ERα in the as as the of A and and showed expression in the A and of the showed the expression of the our results demonstrate a of hADA3 or with ERα in a human hADA3 in to the of pS2 of the coactivator function their to into complexes with transcriptional activators bound to in the of the native chromatin Biochem. Biol. PubMed Scopus Google Scholar, F.J. Oncogene. 2001; 20: PubMed Scopus Google Scholar). directly hADA3 is into transcriptional activator complexes bound to a native we used the analysis of the estrogen-responsive pS2 an or with for and native protein complexes to the The chromatin with and and the associated DNA used as a for the of the pS2 promoter a known C. J. PubMed Scopus Google Scholar). shown in the a and the of in the of the that hADA3 associated with the native pS2 promoter in an ERα in as as in chromatin of and results are with a binding of ER to the pS2 as demonstrated by of estrogen C. J. PubMed Scopus Google Scholar). of of promoter of GAPDH, which is an ER demonstrated the of these results demonstrate that hADA3 a of the activator complexes bound to an estrogen response element in native chromatin ERα ligand hADA3 and the ER-mediated of to an the of hADA3 and to with and the role of ADA3 as a component of the coactivator we examined hADA3 and function as coactivators of transcription by we the and the with hADA3 or with ER in the of and the A of activity in to a or increase in the activity in and the is that of hADA3 or the of ERα in to a hADA3 or increase in ligand-induced activity in of used in showed the expression of hADA3 and ER proteins A and are of ERα and for coactivator function of hADA3 in showed that ERα and transactivation of ERα results demonstrate that hADA3 and function as coactivators for ER-mediated transcriptional activation in mammalian HPV16 E6 the of the of HPV16 E6 to with and the of hADA3 A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google we examined the of E6 on increase in ERα-mediated transactivation of and with hADA3 with E6 or a E6 A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar). hADA3 the activity in A and E6 by on the activity and and and is that of E6 inhibited the increase in activity and and in the hADA3 E6 and A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google the expression of E6 by a in hADA3 A and of the expression of hADA3 and ER proteins A and shown for results demonstrate that HPV16 E6 the coactivator function of hADA3 ERα in human hADA3 the of ERα the results hADA3 function as a coactivator for ER-mediated we to ADA3 enhances the expression of known ER target genes. we the the or hADA3 with or of for RNA and of RNA used to the by a using the for pS2. an increase in pS2 expression in is that the of hADA3 further the ER-mediated increase in pS2 gene expression change in the of the control the of the in using of the hADA3 by the ER further the role of hADA3 as a coactivator for ERα-mediated we a hADA3 or a control RNA a in the expression of endogenous ADA3 is that in the of endogenous hADA3 in a in activity with the control results show a role of endogenous hADA3 in transactivation. of the hADA3 by the of of the ER further the role of endogenous hADA3 in ER we examined the expression of ER target genes cathepsin D, and in of hADA3 using ADA3 we ADA3 in and the increase in expression of ER target genes using A in the expression of ER target genes of ADA3 we examined the of ADA3 on the protein expression of ER cathepsin D, and A inhibition of increase in the of protein expression in hADA3 with control Furthermore, inhibition of progesterone receptor in ADA3 with control these results show a role of endogenous hADA3 in transactivation of genes. HPV16 E6 the in the of ER the of HPV16 E6 to with hADA3, and ADA3 to function as a coactivator for ER-mediated we examined the of E6 on the expression of estrogen target is that a in increase in the of and target of proteins in E6 with The of E6 on is shown in results demonstrate that E6 by targeting a coactivator of ER ER a and ER NRs that control a of physiological (1Greschik H. Moras D. Curr. Top. Med. Chem. 2003; 3: 1573-1599Crossref PubMed Scopus (58) Google Scholar, 2Edwards D.P. J. Mammary Gland Biol. Neoplasia. 2000; 5: 307-324Crossref PubMed Scopus (118) Google Scholar). In that a of and coactivator protein complexes an role in the transcriptional activation function of NRs (7He B. Wilson E.M. Mol. Cell. Biol. 2003; 23: 2135-2150Crossref PubMed Scopus (88) Google Scholar, 8Savkur R.S. Burris T.P. J. Pept. Res. 2004; 63: 207-212Crossref PubMed Scopus (211) Google Scholar). Furthermore, a number of studies have to the of recruitment of distinct of coactivators as a potential of gene expression NRs J.D. Mol. Cell. 2004; Full Text Full Text PDF PubMed Scopus (53) Google Scholar, B.M. R. J. Mol. 2004; PubMed Scopus Google Scholar). studies of mammalian NRs in the yeast have a coactivator role of the conserved as a coactivator of gene expression M. A. R. Genes Dev. 1998; 12: PubMed Scopus Google Scholar, A.E. Gustafsson Mol. Cell. Biol. 1999; PubMed Scopus (60) Google a directly by our of a coactivator role for hADA3, a component of the mammalian in function M. Kumar A. G. G. D. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). that these studies on hADA3 and the of a the of ADA3 to with estrogen receptor A. C. R. Res. PubMed Scopus Google we a of the mammalian ADA3 interaction with ER and the functional role of interaction in the of ectopic as as endogenous The of that the and human ADA3 proteins with estrogen receptor and that endogenous hADA3 an important role in estrogen-induced target gene The results have for the potential role of coactivator complexes in physiological pathways and in oncogenesis. yeast ADA3 as a component of and coactivator complexes been demonstrated to known the mammalian ADA3 function our with our results that hADA3 functions as a coactivator for retinoid receptors in mammalian the by the yeast studies that ADA3 containing complexes as coactivators for nuclear hormone Thus, mammalian as a component of is to an important role in gene expression to a number of important physiological by transcriptional activators of the NR superfamily. results the interaction of human as as the ADA3 with ER are in to a by A. C. R. Res. PubMed Scopus Google in which the to a interaction of ADA3 to The of these to the interaction is the of A. C. R. Res. PubMed Scopus Google Scholar). we the binding using the that these a of a binding using the reverse analysis with and in ER proteins A and Furthermore, the used in for binding with yADA3, which have further the of binding A. C. R. Res. PubMed Scopus Google Scholar). such as p300 and CBP, have activity and directly in chromatin proteins function as coactivators by as of a ADA3 have a is important to which proteins mediate the ADA3 function as a The of as as a gene in complexes J. Y. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google interaction of with D. A. H. Y. Cell. 1999; Full Text Full Text PDF PubMed Scopus Google and the interaction of hADA3 with p300 R. A.E. R.K. J. 2001; 20: PubMed Scopus Google that hADA3 distinct coactivator as also is the in yeast J. N. Mol. Cell. Biol. PubMed Google Scholar). Thus, is that transcriptional activators as of ADA3 coactivator that ADA3 a role in oncogenesis. The interaction with HPV E6 and the of E6 proteins to the hADA3 coactivator function for NR receptors Furthermore, we and have recently shown the hADA3 protein interacts with and functions as a coactivator of transactivation A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar, R. A.E. R.K. J. 2001; 20: PubMed Scopus Google Scholar). The coactivator function of hADA3 also by HPV E6 A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar). The role of known ADA3 retinoid receptors, and estrogen M. Kumar A. G. G. D. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar, R. A.E. R.K. J. 2001; 20: PubMed Scopus Google in and is and these pathways are oncogenesis. Thus, E6 the complexes and influences the transcriptional pathways in which these complexes a a for the role of E6 in oncogenesis. The and been E.M. J. 2003; Scopus Google Scholar). the is been shown that of the transcription of which is in with the an the E.M. J. 2003; Scopus Google Scholar, D.W. Proc. Biol. Med. 1998; PubMed Scopus Google Scholar, C. J. PubMed Scopus Google Scholar, J. Curr. 2004; PubMed Scopus Google Scholar). a estrogen element been to in the promoter of HPV S. R. R. J. PubMed Scopus Google Scholar). also been that HPV E6 and directly with ER and function Biochem. Res. 2003; PubMed Scopus Google Scholar). that E6 target a coactivator of ER a into the by which ER is that E6 also with which as a coactivator for a number of including nuclear hormone receptors H. R. J. 1999; PubMed Google Scholar, D. J. 1999; PubMed Scopus Google Scholar, J. Z. J. Steroid. Biochem. Mol. Biol. 1999; PubMed Scopus Google Scholar). the of HPV E6 binding to p300 on nuclear receptor-mediated transcription been E6 is known to the coactivator function of p300 A. Y. G. M. S. G. H. Mol. Cell. Biol. PubMed Scopus Google Scholar). the important function of ER in and in 2003; PubMed Scopus Google Scholar, 2003; 64: PubMed Scopus Google Scholar, S. J. Mammary Gland Biol. Neoplasia. 2000; 5: PubMed Scopus Google of to expression of hADA3 is or in human including and HPV gene the that such as HPV have an to the function of transcriptional coactivators by studies of the mammalian and their in human these proteins a role in In we have shown that hADA3 and directly with ER, that ADA3 functions as a coactivator for ERα and ERβ-mediated transactivation and enhances the expression of genes, and that HPV E6 ADA3 coactivator function ER, the expression of ER such as and results also the that HPV E6 target transcriptional pathways as a component of oncogenesis. We and for and ER expression and M. for E6