Deletion of PBP/PPARBP, the Gene for Nuclear Receptor Coactivator Peroxisome Proliferator-activated Receptor-binding Protein, Results in Embryonic Lethality

We previously isolated and identified peroxisome proliferator-activated receptor (PPAR)-binding Protein (PBP) as a coactivator for PPARγ. PBP has recently been identified as a component of the multiprotein complexes such as TRAP, DRIP, and ARC that appear to play an important role in the transcriptional activation by several transcriptional factors including nuclear receptors. To assess the biological significance of PBP, we disrupted the PBP gene (PBP/PPARBP) in mice by homologous recombination. PBP+/− mice are healthy, fertile, and do not differ significantly from PBP+/+ control littermates. PBP null mutation (PBP−/−) is embryonically lethal at embryonic day 11.5, suggesting that PBP is an essential gene for mouse embryogenesis. The embryonic lethality is attributed, in part, to defects in the development of placental vasculature similar to those encountered in PPARγ mutants. Transient transfection assays using fibroblasts isolated from PBP mutant embryos revealed a decreased capacity for ligand-dependent transcriptional activation of PPARγ as compared with fibroblasts derived form the wild type embryos. These observations suggest that there is no functional redundancy between PBP and other coactivators such as steroid receptor coactivator-1 and that PBP plays a critical role in the signaling of PPARγ and other nuclear receptors. We previously isolated and identified peroxisome proliferator-activated receptor (PPAR)-binding Protein (PBP) as a coactivator for PPARγ. PBP has recently been identified as a component of the multiprotein complexes such as TRAP, DRIP, and ARC that appear to play an important role in the transcriptional activation by several transcriptional factors including nuclear receptors. To assess the biological significance of PBP, we disrupted the PBP gene (PBP/PPARBP) in mice by homologous recombination. PBP+/− mice are healthy, fertile, and do not differ significantly from PBP+/+ control littermates. PBP null mutation (PBP−/−) is embryonically lethal at embryonic day 11.5, suggesting that PBP is an essential gene for mouse embryogenesis. The embryonic lethality is attributed, in part, to defects in the development of placental vasculature similar to those encountered in PPARγ mutants. Transient transfection assays using fibroblasts isolated from PBP mutant embryos revealed a decreased capacity for ligand-dependent transcriptional activation of PPARγ as compared with fibroblasts derived form the wild type embryos. These observations suggest that there is no functional redundancy between PBP and other coactivators such as steroid receptor coactivator-1 and that PBP plays a critical role in the signaling of PPARγ and other nuclear receptors. steroid receptor coactivator peroxisome proliferator-activated receptor PPAR-binding protein polymerase chain reaction reverse transcriptase-PCR embryonic day embryonic stem cells thyroid hormone receptor-associated protein vitamin D3 receptor interacting protein activator recruited cofactor CREB-binding protein The transcriptional activation of nuclear receptors involves the participation of cofactors termed nuclear receptor corepressors and coactivators (1.Xu L. Glass C.K. Rosenfeld M.G. Curr. Opin. Genet. Dev. 1999; 9: 140-147Crossref PubMed Scopus (815) Google Scholar, 2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar). The coactivators identified in recent years include, among others: the SRC-11 family, with three members (SRC-1 (3.Onate S.A. Tsai S.Y. Tsai M.J. O'Malley B.W. Science. 1995; 270: 1354-1357Crossref PubMed Scopus (2063) Google Scholar, 4.Kamei Y. Xu L. Heinzel T. Torchia J. Kurokawa R. Gloss B. Lin S.C. Heyman R.A. Rose D.W. Glass C.K. Rosenfeld M.G. Cell. 1996; 85: 403-414Abstract Full Text Full Text PDF PubMed Scopus (1928) Google Scholar, 5.Zhu Y. Qi C. Calandra C. Rao M.S. Reddy J.K. Gene Expr. 1996; 6: 185-195PubMed Google Scholar), SRC-2 (TIF-2/GRIP-1 (6.Voegel J.J. Heine M.J.S. Zechel C. Chambon P. Gronemeyer H. EMBO J. 1996; 15: 3667-3675Crossref PubMed Scopus (953) Google Scholar)), and SRC-3 (ACTR (7.Chen H. Lin R.J. Schiltz R.L. Chkravarti D. Nash A. Nagy L. Privalsky M.L. Nakatani Y. Evans R.M. Cell. 1997; 90: 569-580Abstract Full Text Full Text PDF PubMed Scopus (1270) Google Scholar), AIB (8.Anzick S.L. Kononen J. Walker R.L. Azorsa D.O. Tanner M.M. Guan X.Y. Sauter G. Kallioniemi O.P. Trent J.M. Meltzer P.S. Science. 1997; 277: 965-968Crossref PubMed Scopus (1436) Google Scholar), p/CIP (9.Torchia J. Rose D.W. Inostroza J. Kamei Y. Westin S. Glass C.K. Rosenfeld M.G. Nature. 1997; 387: 677-684Crossref PubMed Scopus (1108) Google Scholar))); p300/CBP (4.Kamei Y. Xu L. Heinzel T. Torchia J. Kurokawa R. Gloss B. Lin S.C. Heyman R.A. Rose D.W. Glass C.K. Rosenfeld M.G. Cell. 1996; 85: 403-414Abstract Full Text Full Text PDF PubMed Scopus (1928) Google Scholar); PBP (10.Zhu Y. Qi C. Jain S. Rao M.S. Reddy J.K. J. Biol. Chem. 1997; 272: 25500-25506Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar); and PGC-1 (11.Puigserver P. Wu Z. Park C.W. Graves R. Wright M. Spiegelman B.M. Cell. 1998; 92: 829-839Abstract Full Text Full Text PDF PubMed Scopus (3102) Google Scholar) (see Refs.1.Xu L. Glass C.K. Rosenfeld M.G. Curr. Opin. Genet. Dev. 1999; 9: 140-147Crossref PubMed Scopus (815) Google Scholar and 2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar for review). The recruitment of most of these proteins to activated receptors is mediated in most part by LXXLL motifs present in these coactivators, which have been shown to be necessary and sufficient for the interaction with nuclear receptors (9.Torchia J. Rose D.W. Inostroza J. Kamei Y. Westin S. Glass C.K. Rosenfeld M.G. Nature. 1997; 387: 677-684Crossref PubMed Scopus (1108) Google Scholar, 12.Heery D.M. Kalkhoven E. Hoare S. Parker M.G. Nature. 1997; 387: 733-736Crossref PubMed Scopus (1778) Google Scholar). The mechanisms underlying the transcriptional regulation by coactivators are just beginning to emerge. Some of these coactivators, such as p300/CBP, SRC-1, and ACTR, possess intrinsic histone acetyltransferase activity and modify the chromatin organization of the target gene promoter regions (13.Bannister A.J. Kouzarides T. Nature. 1996; 384: 641-643Crossref PubMed Scopus (1535) Google Scholar). Others, such as PBP (14.Yuan C.X. Ito M. Fondell J.D. Fu Z.Y. Roeder R.G. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 7939-7944Crossref PubMed Scopus (391) Google Scholar), with no histone acetyltransferase activity, constitute an integral part of the multiprotein complexes that appear to act more directly on the transcriptional apparatus, presumably after the unwinding of chromatin (1.Xu L. Glass C.K. Rosenfeld M.G. Curr. Opin. Genet. Dev. 1999; 9: 140-147Crossref PubMed Scopus (815) Google Scholar, 2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar). PBP was initially isolated and characterized by us as a coactivator for PPARγ and like other nuclear receptor coactivators, it contains LXXLL signature motifs in the region that interacts with nuclear receptors (10.Zhu Y. Qi C. Jain S. Rao M.S. Reddy J.K. J. Biol. Chem. 1997; 272: 25500-25506Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar). Subsequently, PBP has been found to be a critical component of the thyroid hormone receptor-associated proteins (TRAPs) (14.Yuan C.X. Ito M. Fondell J.D. Fu Z.Y. Roeder R.G. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 7939-7944Crossref PubMed Scopus (391) Google Scholar), vitamin D3 receptor interacting protein (DRIP) complex (15.Rachez C. Lemon B.D. Suldan Z. Bromleigh V. Gamble M. Naar A.M. Erdjument-Bromage H. Tempst P. Freedman L.P. Nature. 1999; 398: 824-828Crossref PubMed Scopus (637) Google Scholar), and activator-recruited cofactor (ARC) complex (16.Naar A.M. Beaurang P.A. Zhou S. Abraham S. Solomon W. Tjian R. Nature. 1999; 398: 828-832Crossref PubMed Scopus (374) Google Scholar). PBP, which is variously designated as TRAP220 (14.Yuan C.X. Ito M. Fondell J.D. Fu Z.Y. Roeder R.G. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 7939-7944Crossref PubMed Scopus (391) Google Scholar), DRIP205 (15.Rachez C. Lemon B.D. Suldan Z. Bromleigh V. Gamble M. Naar A.M. Erdjument-Bromage H. Tempst P. Freedman L.P. Nature. 1999; 398: 824-828Crossref PubMed Scopus (637) Google Scholar), and CRSP210 (16.Naar A.M. Beaurang P.A. Zhou S. Abraham S. Solomon W. Tjian R. Nature. 1999; 398: 828-832Crossref PubMed Scopus (374) Google Scholar) in these complexes, appears to be the major anchor for bridging various subunits with the liganded nuclear receptor (2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar). More recently, we found PBP gene overexpression and amplification in a significant proportion of breast cancers (17.Zhu Y. Qi C. Jain S. Le Beau M.M. Espinosa III, R. Atkins G.B. Lazar M.A. Yeldandi A.V. Rao M.S. Reddy J.K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 10848-10853Crossref PubMed Scopus (150) Google Scholar), further underscoring the critical importance of this coactivator in the transcriptional activation (2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar). Nevertheless, our knowledge regarding the function of PBP, and of other nuclear receptor coactivators, is based largely on the results fromin vitro binding assays and transient transfection experiments. There is very little information regarding the in vivo function of PBP and whether a redundancy exists between the biological functions of PBP and of other coactivator molecules. For example, SRC-1 with its histone acetyltransferase activity has been found to be a crucial coactivator under in vitro conditions (3.Onate S.A. Tsai S.Y. Tsai M.J. O'Malley B.W. Science. 1995; 270: 1354-1357Crossref PubMed Scopus (2063) Google Scholar), whereas mice deficient in SRC-1 appeared essentially normal, implying redundancy in nuclear receptor coactivator functions (18.Xu J. Qiu Y. DeMayo F.J. Tsai M.J. O'Malley B.W. Science. 1998; 279: 1922-1925Crossref PubMed Scopus (599) Google Scholar, 19.Qi C. Zhu Y. Pan J. Yeldandi A.V. Rao M.S. Maeda N. Subbarao V. Pulikuri S. Hashimoto T. Reddy J.K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 1585-1590Crossref PubMed Scopus (70) Google Scholar). We now show, that in contrast to SRC-1 gene deletion, the PBP gene deletion in mice is embryonic lethal after 11.5 days post coitus. Our data also demonstrate that the PBP gene is important for establishing embryonic vascular network in the placenta; the placental defect in PBP−/− mutants shares a great similarity with that occurring in PPARγ-deficient mice. The genomic DNA fragment containing the full-length PBP gene was obtained by screening a mouse 129/Sv P1 bacteriophage library (Genome Systems, St. Louis, MO) using polymerase chain reaction with primers 5′-CTCAGAGTGCCCTCTTTGAT-3′ and 5′-TCCCTAATTCTCCAGTGGTC-3′ designed from mouse PBP cDNA sequence (10.Zhu Y. Qi C. Jain S. Rao M.S. Reddy J.K. J. Biol. Chem. 1997; 272: 25500-25506Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar). A 2.3-kilobase fragment extending from nucleotide position 38 of exon 10 into intron 11 and a 3.0-kilobase fragment from intron 14 to nucleotide position 19 of exon 16 were inserted into the pPNT targeting vector. The targeting vector contained the phosphoglycerate kinase promoter/neomycin gene (Neo), as well as the herpes simplex thymidine kinase (hsv-tk) gene to allow the use of a positive-negative selection scheme. The final targeting construct, designated pPNT-PBP, is illustrated in Fig. 1 A. The NotI-linearized targeting vector (40 μg) was electroporated into HM1 embryonic stem (ES) cells (20.Selfridge J. Pow A.M. McWhir J. Magin T.M. Melton D.W. Somatic Cell Mol. Genet. 1992; 18: 325-336Crossref PubMed Scopus (93) Google Scholar) and selected in a medium containing 200 μg/ml G418 and 2 μm ganciclovir. Surviving colonies were screened for homologous recombination event by PCR with two pairs of primers, P1/P2 and P3/P4. Although P2 (5′-CCTCTGTTCCACATACACTTC-3′) and P3 (5′-TCCAGACTGCCTTGGGAAAA-3′) are located in the neomycin gene, primers P1 (5′-GCTCCCTTGGATAAGATT-3′) and P4 (5′-CTTTGAACAACTTTGGCAATGAA-3′) are located in exons 9 and 16, respectively, outside the homologous recombinant region (Fig. 1 A). Two positive ES cell clones among 120 were identified and injected into 3.5-day-old C57BL/6 blastocysts. Chimeric male mice obtained were then bred to C57BL/6 females to produce F1 heterozygous mice, which were then interbred. DNA from embryos and from the tail tips of 3-week-old mice was genotyped by PCR amplification using primer pair P7 (5′-CCTTCTTTCTCCGCAGTCAC-3′) from exon 12 and P8 (5′-AGTGATGAGTTCATACAGGGG-3′) from exon 13 to detect the wild type allele (Fig. 1, A and D) and primer pair P5 (5′-CCACAGTCGATGAATCCAGAA-3′) and P6 (5′-TGAATGAACTGCAGGACGAGG-3′) from the neomycin cassette to detect the targeted allele. For light microscopy, tissues were fixed overnight in 4% paraformaldehyde and embedded in paraffin. Sections (4 μm thick) were stained with hematoxylin and eosin. For electron microscopy, whole E10.5 placentas were fixed overnight in cold 3% glutaraldehyde, washed, and post-fixed with 1% osmium tetroxide. Thin sections were contrasted with uranyl acetate and lead citrate and using a electron at E10.5 embryos were from the and into was with of with at for 10 cells were and the in the medium was with an of were by in and then on a in medium with and 2 The cells were at at under the cells were using the to the and were as previously (14.Yuan C.X. Ito M. Fondell J.D. Fu Z.Y. Roeder R.G. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 7939-7944Crossref PubMed Scopus (391) Google Scholar). vector was as a as a control for transfection Cell were after transfection and were for and from fibroblasts using was in the PCR was using a pair of primers, from exon and from exon for from fibroblasts isolated from E10.5 embryos were to using as (17.Zhu Y. Qi C. Jain S. Le Beau M.M. Espinosa III, R. Atkins G.B. Lazar M.A. Yeldandi A.V. Rao M.S. Reddy J.K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 10848-10853Crossref PubMed Scopus (150) Google Scholar). PBP contains two LXXLL signature motifs located at and respectively, which are necessary and sufficient for interaction between coactivators and nuclear receptors (9.Torchia J. Rose D.W. Inostroza J. Kamei Y. Westin S. Glass C.K. Rosenfeld M.G. Nature. 1997; 387: 677-684Crossref PubMed Scopus (1108) Google Scholar, Y. Qi C. Jain S. Rao M.S. Reddy J.K. J. Biol. Chem. 1997; 272: 25500-25506Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar, 12.Heery D.M. Kalkhoven E. Hoare S. Parker M.G. Nature. 1997; 387: 733-736Crossref PubMed Scopus (1778) Google Scholar). this region of the PBP gene the interaction of PBP with PPARγ and other nuclear receptors. The targeting vector was designed to exons and this region with the phosphoglycerate there is a between exons 11 and the of PBP from to the be ES cells were electroporated with targeting and to positive and the mutant allele were identified by PCR of the recombinant these cells were then to produce mice heterozygous for the PBP that between wild type and PBP+/− mice in the of PBP+/− heterozygous for the gene were and from wild type littermates. the PBP+/− were no mutant mice were found among a significant compared with the whereas PBP+/+ and were found at a To the of we genotyped the embryos at PBP−/− embryos were at embryonic day and E10.5 and at PBP−/− embryos were and at the of Although the was in a of were to The PBP−/− embryos at were in and compared with the wild type and heterozygous (Fig. 1 of embryos days E10.5 and revealed such as of the as compared with wild type embryos not lethality of PBP null of in a the embryonic vascular network in the is essential for the development of embryos. that embryonic lethality in PPARγ mutants E10.5 is a of placental vascular defects Y. A. Evans R. Mol. Cell. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). as the PBP mutation is lethal we that vascular defects in PBP null PBP as a coactivator for PPARγ (14.Yuan C.X. Ito M. Fondell J.D. Fu Z.Y. Roeder R.G. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 7939-7944Crossref PubMed Scopus (391) Google Scholar). The of PBP, PPARγ PBP null we found in the and vascular compared with wild type placentas (Fig. the of the wild type is of of cells and a network of with A). contrast to the of in the of wild type and heterozygous the in the PBP mutant was with a network of embryonic (Fig. 2 of cells with were in the PBP null (Fig. 2 of placental the and between the and the the III, which the is in as compared with and PBP null of the between and vasculature is of the of (Fig. 2 these PBP mutant there is of activity of the cells (Fig. 2 which is also an of vascular To demonstrate that the homologous recombination in the PBP gene results in the of PBP, we PBP with using from fibroblasts derived from PBP−/− embryos. PBP was present in fibroblasts derived from the wild type not in fibroblasts isolated from PBP−/− embryos A). was further by as it no PBP protein in PBP−/− cells (Fig. a nuclear receptor PBP has been shown to of nuclear receptors under in vitro conditions (10.Zhu Y. Qi C. Jain S. Rao M.S. Reddy J.K. J. Biol. Chem. 1997; 272: 25500-25506Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar, C.X. Ito M. Fondell J.D. Fu Z.Y. Roeder R.G. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 7939-7944Crossref PubMed Scopus (391) Google Scholar, Y. Qi C. Jain S. Le Beau M.M. Espinosa III, R. Atkins G.B. Lazar M.A. Yeldandi A.V. Rao M.S. Reddy J.K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 10848-10853Crossref PubMed Scopus (150) Google Scholar). We PPARγ and function in fibroblasts derived from PBP null embryos to the function of these nuclear receptors in the of were isolated from wild type and PBP−/− mouse embryos at E10.5 and transcriptional of PPARγ and were by the receptor with a Although PPARγ demonstrate a ligand-dependent transcriptional activity in PBP+/− and PBP−/− the activity was that by fibroblasts derived from wild type embryos (Fig. results were obtained with and transcriptional activation of in PBP null isolated from wild type heterozygous and (PBP−/−) mouse embryos were with of of and of in the of The activity obtained on transfection of the in the of with from wild type mouse was as are the of and are to the of for was in the as for using and as an important role for PBP as a coactivator for PPARγ and for other nuclear receptors (10.Zhu Y. Qi C. Jain S. Rao M.S. Reddy J.K. J. Biol. Chem. 1997; 272: 25500-25506Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar, C.X. Ito M. Fondell J.D. Fu Z.Y. Roeder R.G. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 7939-7944Crossref PubMed Scopus (391) Google Scholar, Y. Qi C. Jain S. Le Beau M.M. Espinosa III, R. Atkins G.B. Lazar M.A. Yeldandi A.V. Rao M.S. Reddy J.K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 10848-10853Crossref PubMed Scopus (150) Google Scholar). PBP has also recently as a in a multiprotein coactivator complex which has been in to be for transcriptional activity of nuclear receptors and other such as and (2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar, C.X. Ito M. Fondell J.D. Fu Z.Y. Roeder R.G. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 7939-7944Crossref PubMed Scopus (391) Google Scholar, C. Lemon B.D. Suldan Z. Bromleigh V. Gamble M. Naar A.M. Erdjument-Bromage H. Tempst P. Freedman L.P. Nature. 1999; 398: 824-828Crossref PubMed Scopus (637) Google Scholar, A.M. Beaurang P.A. Zhou S. Abraham S. Solomon W. Tjian R. Nature. 1999; 398: 828-832Crossref PubMed Scopus (374) Google Scholar). multiprotein histone acetyltransferase activity, to the nuclear PBP, implying that the PBP is a of the nuclear receptor signaling (1.Xu L. Glass C.K. Rosenfeld M.G. Curr. Opin. Genet. Dev. 1999; 9: 140-147Crossref PubMed Scopus (815) Google B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar). this using homologous we demonstrate that PBP is for embryonic development a of this protein to embryonic of These observations the of redundancy between PBP function and that of of the nuclear receptor The that mice for the disrupted PBP gene of the embryonic that PBP is not essential for the of and at the of The to this that PBP is essential for the of mouse embryogenesis. The of embryos at has been encountered in a of null by gene targeting A.J. Genet. 1995; Full Text PDF PubMed Scopus Google Scholar). For example, mice for J. P. V. L. Dev. 1992; 6: PubMed Scopus Google Scholar), PPARγ Y. A. Evans R. Mol. Cell. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar), and V. P. C. P. Chambon P. Dev. Biol. 1997; PubMed Scopus Google Scholar) and of these in PPARγ and V. P. C. P. Chambon P. Dev. Biol. 1997; PubMed Scopus Google Scholar), which to embryonic To whether the in the of the PBP−/− embryos is the of placental sections of were by light and electron in PBP−/− are to into suggesting a of These defects to and of PBP−/− embryos. These observations the at the essential function of PBP in the development of the More the by the PBP−/− shares a similarity at the and with the PPARγ Y. A. Evans R. Mol. Cell. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar) and V. P. C. P. Chambon P. Dev. Biol. 1997; PubMed Scopus Google Scholar) null The in placental defects the in vivo to the role of PBP as coactivator for PPARγ and PPARγ was in the beginning at the placental defects in the of PPARγ the of the null embryos at E10.5 Y. A. Evans R. Mol. Cell. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). PBP was in the mouse beginning at and its was in at (10.Zhu Y. Qi C. Jain S. Rao M.S. Reddy J.K. J. Biol. Chem. 1997; 272: 25500-25506Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar). PBP mutation the function of PPARγ and other critical nuclear receptors at this coactivators isolated to with nuclear receptors and under in vitro with SRC-1, in which vivo function be by other coactivators (18.Xu J. Qiu Y. DeMayo F.J. Tsai M.J. O'Malley B.W. Science. 1998; 279: 1922-1925Crossref PubMed Scopus (599) Google Scholar, 19.Qi C. Zhu Y. Pan J. Yeldandi A.V. Rao M.S. Maeda N. Subbarao V. Pulikuri S. Hashimoto T. Reddy J.K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 1585-1590Crossref PubMed Scopus (70) Google Scholar), our results now that the of PBP be by other PBP gene from that of SRC-1 gene in that mice null for SRC-1 are and (18.Xu J. Qiu Y. DeMayo F.J. Tsai M.J. O'Malley B.W. Science. 1998; 279: 1922-1925Crossref PubMed Scopus (599) Google Scholar, 19.Qi C. Zhu Y. Pan J. Yeldandi A.V. Rao M.S. Maeda N. Subbarao V. Pulikuri S. Hashimoto T. Reddy J.K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 1585-1590Crossref PubMed Scopus (70) Google Scholar); this a functional redundancy of activity be by similar coactivators such as (7.Chen H. Lin R.J. Schiltz R.L. Chkravarti D. Nash A. Nagy L. Privalsky M.L. Nakatani Y. Evans R.M. Cell. 1997; 90: 569-580Abstract Full Text Full Text PDF PubMed Scopus (1270) Google Scholar), (4.Kamei Y. Xu L. Heinzel T. Torchia J. Kurokawa R. Gloss B. Lin S.C. Heyman R.A. Rose D.W. Glass C.K. Rosenfeld M.G. Cell. 1996; 85: 403-414Abstract Full Text Full Text PDF PubMed Scopus (1928) Google Scholar), and (1.Xu L. Glass C.K. Rosenfeld M.G. Curr. Opin. Genet. Dev. 1999; 9: 140-147Crossref PubMed Scopus (815) Google Scholar, 2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar). The mechanisms for nuclear receptor transcriptional activation for a chromatin complexes such as and are recruited to the of chromatin (2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar), which is by complexes such as with histone acetyltransferase activity for further chromatin (13.Bannister A.J. Kouzarides T. Nature. 1996; 384: 641-643Crossref PubMed Scopus (1535) Google Scholar). The then the recruitment of complexes with PBP as an anchor for the of (2.Lemon B.D. Freedman L.P. Curr. Opin. Genet. Dev. 1999; 9: 499-504Crossref PubMed Scopus (90) Google Scholar). contrast to the embryonic lethality of PBP null the PBP null at a ligand-dependent activation of PPARγ and transcriptional activity under the in the transient are not into of a and are We for on mouse embryos and S. of the for in ES cell