Promyelocytic Leukemia Protein (PML) Functions as a Glucocorticoid Receptor Co-activator by Sequestering Daxx to the PML Oncogenic Domains (PODs) to Enhance Its Transactivation Potential

Abstract

Daxx has been reported to function as a transcriptional modulator in the nucleus. In the present study, we have explored the role of Daxx in regulating the transcriptional activity of the glucocorticoid receptor (GR). Overexpression of Daxx suppressed GR-mediated activation of the mouse mammary tumor virus promoter in COS-1, HeLa, and 293T cells. In vitro and in vivo studies revealed that Daxx could directly bind to GR. The mapping analysis further demonstrated that the C-terminal region of Daxx-(501–740) mediates the interaction and transcriptional repression of GR. The repressive effect of Daxx and Daxx-(501–740) on GR could be alleviated by co-expression of promyelocytic leukemia protein (PML). Furthermore, immunofluorescence analysis showed that overexpression of wild-type PML results in the translocation of Daxx and Daxx-(501–740) to the PML oncogenic domains (PODs). By contrast, a PML sumoylation-defective mutant failed to recruit Daxx to PODs and to reverse the Daxx repression effect on GR. Accordingly, As2O3 treatment rendered the sequestration of endogenous Daxx to the PODs, leading to an enhancement of GR transactivation in COS-1 cells. Taken together, these findings suggest that recruitment of Daxx into the subnuclear POD structures sequesters it from the GR/co-activators complex, thereby alleviating its repressive effects. Our present studies provide the important link between Daxx/PML interaction and GR transcriptional activation. Daxx has been reported to function as a transcriptional modulator in the nucleus. In the present study, we have explored the role of Daxx in regulating the transcriptional activity of the glucocorticoid receptor (GR). Overexpression of Daxx suppressed GR-mediated activation of the mouse mammary tumor virus promoter in COS-1, HeLa, and 293T cells. In vitro and in vivo studies revealed that Daxx could directly bind to GR. The mapping analysis further demonstrated that the C-terminal region of Daxx-(501–740) mediates the interaction and transcriptional repression of GR. The repressive effect of Daxx and Daxx-(501–740) on GR could be alleviated by co-expression of promyelocytic leukemia protein (PML). Furthermore, immunofluorescence analysis showed that overexpression of wild-type PML results in the translocation of Daxx and Daxx-(501–740) to the PML oncogenic domains (PODs). By contrast, a PML sumoylation-defective mutant failed to recruit Daxx to PODs and to reverse the Daxx repression effect on GR. Accordingly, As2O3 treatment rendered the sequestration of endogenous Daxx to the PODs, leading to an enhancement of GR transactivation in COS-1 cells. Taken together, these findings suggest that recruitment of Daxx into the subnuclear POD structures sequesters it from the GR/co-activators complex, thereby alleviating its repressive effects. Our present studies provide the important link between Daxx/PML interaction and GR transcriptional activation. glucocorticoid receptor 58-kDa microspherule protein dexamethasone promyelocytic leukemia protein PML oncogenic domains small ubiquitin-like modifier CREB binding protein fetal bovine serum glutathione S-transferase 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside hemagglutinin 4′,6-diamidino-2-phenylindole murine mammary tumor virus The glucocorticoid receptor (GR),1 a member of the ligand-dependent nuclear receptor superfamily, plays important roles in governing development, growth, apoptosis, and anti-inflammatory processes (1Barnes P.J. Clin. Sci. (Lond). 1998; 94: 557-572Crossref PubMed Scopus (1250) Google Scholar, 2Sapolsky R.M. Romero L.M. Munck A.U. Endocr. Rev. 2000; 21: 55-89Crossref PubMed Scopus (5857) Google Scholar, 3Adcock I.M. Pulm. Pharmacol. Ther. 2001; 14: 211-219Crossref PubMed Scopus (143) Google Scholar, 4Almawi W.Y. Melemedjian O.K. J. Leukoc. Biol. 2002; 71: 9-15PubMed Google Scholar, 5Distelhorst C.W. Cell Death Differ. 2002; 9: 6-19Crossref PubMed Scopus (274) Google Scholar). Like other superfamily members, GR contains the N-terminal transactivation domain, central DNA binding domain, and the C-terminal ligand binding domain (6Olefsky J.M. J. Biol. Chem. 2001; 276: 36863-36864Abstract Full Text Full Text PDF PubMed Scopus (245) Google Scholar). Prior to exposure to its respective ligand, the GR and other receptors in this family form complexes with heat shock proteins (HSPs), restricting the unliganded-receptor in its inactive state. Upon ligand binding, the receptor is dissociated from HSPs and translocates to the nucleus where the liganded receptor binds to the glucocorticoid-responsive element and recruits co-factors to regulate transcription (7Beato M. Sanchez-Pacheco A. Endocr. Rev. 1996; 17: 587-609Crossref PubMed Scopus (357) Google Scholar). A diverse group of proteins have emerged as potential cofactors for nuclear receptors through direct protein-protein interactions. For instances, several co-activators have been identified that bind to GR and modulate GR transcriptional activity, including CBP/p300, p160 family co-activators (SRC-1, GRIP1, and p/CIP), and chromatin remodeling complexes (BRG-1 (SWI/SNF) complex and P/CAF (ADA/SAGA) complex) (8Robyr D. Wolffe A.P. Wahli W. Mol. Endocrinol. 2000; 14: 329-347Crossref PubMed Scopus (325) Google Scholar, 9Rosenfeld M.G. Glass C.K. J. Biol. Chem. 2001; 276: 36865-36868Abstract Full Text Full Text PDF PubMed Scopus (437) Google Scholar). These co-activators appear to be assembled in a multiprotein complex, facilitating the access of nuclear receptors and the RNA polymerase II core machinery to their target DNA by a chromatin remodeling process (10Collingwood T.N. Urnov F.D. Wolffe A.P. J. Mol. Endocrinol. 1999; 23: 255-275Crossref PubMed Scopus (270) Google Scholar). In addition to regulating GR transcriptional activity via direct protein-protein interactions, some co-factors appear to modulate GR activity through indirect fashion. PML, a protein located at the promyelocytic oncogenic domains (PODs), has previously been reported to stimulate GR and RXRα transcriptional activity through its interaction with CBP (11Doucas V. Tini M. Egan D.A. Evans R.M. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 2627-2632Crossref PubMed Scopus (155) Google Scholar). These results demonstrated that a portion of CBP is recruited to the PODs through its association with PML, suggesting that PML and/or POD-associated proteins may function as an important cofactor in governing nuclear hormone receptor transcriptional activity and function. Besides PML and CBP, several cellular proteins have been reported to be associated with PODs, including Sp100, Daxx, p53, Rb, small ubiquitin-like modifier (SUMO-1), and BLM (12Hatta M. Fukamizu A. Science's STKE. 2001; (http://stke.sciencemag.org/cgi/content/full/sigtrans;2001/112/e1)PubMed Google Scholar, 13Borden K.L. Mol. Cell. Biol. 2002; 22: 5259-5269Crossref PubMed Scopus (263) Google Scholar). Results from many elegant studies have revealed that overexpression of p53 suppressed GR-mediated reporter gene activation (14Yu C. Yap N. Chen D. Cheng S. Cancer Lett. 1997; 116: 191-196Crossref PubMed Scopus (30) Google Scholar, 15Sengupta S. Vonesch J.L. Waltzinger C. Zheng H. Wasylyk B. EMBO J. 2000; 19: 6051-6064Crossref PubMed Scopus (90) Google Scholar) and Rb potentiated GR transcriptional activity through its interaction with hBRM (16Singh P. Chan S.W. Hong W. J. Biol. Chem. 2001; 276: 13762-13770Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar), respectively. Recently, SUMO-1 modification of GR has been shown to regulate its transcriptional activity (17Le Drean Y. Mincheneau N. Le Goff P. Michel D. Endocrinology. 2002; 143: 3482-3489Crossref PubMed Scopus (134) Google Scholar, 18Tian S. Poukka H. Palvimo J.J. Janne O.A. Biochem. J. 2002; 367: 907-911Crossref PubMed Scopus (137) Google Scholar). These findings suggest that POD-associated proteins play important roles in modulating GR transcriptional activity. Whether other POD-associated proteins are also involved in regulating GR transcriptional activity remains to be explored. Daxx, a PODs-associated protein, was identified as an interacting protein of PML (19Torii S. Egan D.A. Evans R.A. Reed J.C. EMBO J. 1999; 18: 6037-6049Crossref PubMed Scopus (236) Google Scholar, 20Ishov A.M. Sotnikov A.G. Negorev D. Vladimirova O.V. Neff N. Kamitani T. Yeh E.T. Strauss III, J.F. Maul G.G. J. Cell Biol. 1999; 147: 221-234Crossref PubMed Scopus (694) Google Scholar, 21Li H. Leo C. Zhu J. Wu X. O'Neil J. Park E.J. Chen J.D. Mol. Cell. Biol. 2000; 20: 1784-1796Crossref PubMed Scopus (309) Google Scholar). Recent studies implied that Daxx might function as a transcriptional coregulator. Daxx has been shown to exhibit transcriptional repression activity by inhibiting the transcription factor Pax3 and ETS1 through direct protein-protein interactions (22Hollenbach A.D. Sublett J.E. McPherson C.J. Grosveld G. EMBO J. 1999; 18: 3702-3711Crossref PubMed Scopus (185) Google Scholar, 23Li R. Pei H. Watson D.K. Papas T.S. Oncogene. 2000; 19: 745-753Crossref PubMed Scopus (161) Google Scholar). Most recently, Emelyanov et al.reported that Daxx acts as a transcriptional co-activator or co-repressor of Pax5 in different cellular contexts (24Emelyanov A.V. Kovac C.R. Sepulveda M.A. Birshtein B.K. J. Biol. Chem. 2002; 277: 11156-11164Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). Although the exact mechanism accounting for these observations is still unclear, the recruitment of nuclear factors possessing either histone acetyltransferase or histone deacetylase activity by Daxx to modulate Pax5 transcriptional activity was proposed (24Emelyanov A.V. Kovac C.R. Sepulveda M.A. Birshtein B.K. J. Biol. Chem. 2002; 277: 11156-11164Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). In addition, the transcriptional repression effect of Daxx could be modulated by subnuclear compartmentalization through protein-protein interactions. We have recently demonstrated that overexpression of a nucleolar protein MSP58 alleviates the transcriptional repression elicited by Daxx, correlating well with sequestration of Daxx to the nucleolus via Daxx/MSP58 protein-protein interactions (25Lin D.Y. Shih H.M. J. Biol. Chem. 2002; 277: 25446-25456Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar). Furthermore, Lehembreet al. has shown that SUMO-1-modified PML could relieve the transrepression effect of Daxx on Pax3 transcriptional activity through sequestering Daxx into the PODs (26Lehembre F. Muller S. Pandolfi P.P. Dejean A. Oncogene. 2001; 20: 1-9Crossref PubMed Scopus (94) Google Scholar). Taken together, PML may exert its regulatory effect on transcription factor(s) through altering the compartmentalization of Daxx or other co-regulator(s). This notion led us to raise a question as to whether GR is also regulated by PML, at least in part, through Daxx sequestration to the PODs. In the present study, we have characterized both biochemical and functional interactions between Daxx and GR. Furthermore, the Daxx-mediated GR repression could be alleviated by the co-expression of wild-type PML but not by a sumoylation-defective PML mutant, which also fails to recruit Daxx to the PODs. Our findings thus provide the first evidence that Daxx could modulate the transcriptional activity of nuclear hormone receptor through protein-protein interactions and sheds light on the mechanism underlying the PML role in modulating nuclear hormone receptor function. LexA-Daxx, its deletion mutants LexA-MST3, LexA-lamin, HA-Daxx, and its derived mutant constructs have been described before (25Lin D.Y. Shih H.M. J. Biol. Chem. 2002; 277: 25446-25456Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar). A mammalian GST-Daxx expression vector was generated by insertion of Daxx into pDEST 26 (Invitrogen). MMTV-Luc and pCMX-PML were kind gifts from Drs. Chawnshang Chang and Ronald Evan, respectively. pGal-AD-GR was engineered by inserting GR region into the of vector which the activation domain a at and was in of on the was by to the were as described (25Lin D.Y. Shih H.M. J. Biol. Chem. 2002; 277: 25446-25456Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar). was first with and by the were on and for were further for activity. were with of and as The were from to the of the mammalian were from the COS-1, HeLa, and 293T were in with fetal bovine serum and were into the before were a (Invitrogen). the were for and For the reporter were on for to with A of of DNA were including expression as an for of were in the with or dexamethasone and/or further treatment of Cell were and for activity for the reporter and activity for the as the For of and GST-Daxx 293T were with or were in and and at for at were with for at The proteins were by by GR protein was with the proteins were with or which of protein in of binding and for and by and the interaction in mammalian wild-type GR with Daxx expression was into COS-1 by the were in of and Cell were with Daxx or GR and the were on protein of proteins were as described previously (25Lin D.Y. Shih H.M. J. Biol. Chem. 2002; 277: 25446-25456Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar). The was from COS-1 were the before The expression of Daxx or its deletion mutants or GR with PML or PML sumoylation-defective mutant were into COS-1 cells. the and were for an in the or of or were in in and with The were with an and an for at this were for with at and at with and for at were revealed by The were on and with were a whether Daxx is involved in regulating GR transcriptional the Daxx expression was into COS-1 with the GR expression and the MMTV-Luc shown in Daxx suppressed GR-mediated transactivation in a fashion. By contrast, a transcriptional GRIP1, potentiated the transactivation of GR. Furthermore, the repressive effect of Daxx on GR was also in other as and 293T that the GR repression is not a whether the transcriptional repression of GR by Daxx is through the direct protein-protein interaction between Daxx and we first the COS-1 were with expression constructs GR and and by treatment of were to with an by with an shown in Daxx was in the complexes of GR This interaction was also in a not These results suggest that Daxx and GR to form complexes in mammalian cells. further whether this association is through direct protein-protein were GST-Daxx protein and in vitro GR. shown in GR was by GST-Daxx but not by protein, that GR binds to Daxx be that the interaction between GR and Daxx was not by the or of further the direct protein-protein interaction between Daxx and we also the The GR was in into vector and with different proteins and for the to and reporter in with and was to form in the a interaction between GR and this interaction is interaction between GR and or was The interaction was further by Taken together, results demonstrated that GR with Daxx through direct protein-protein interactions. the of Daxx that is involved in deletion constructs of Daxx were engineered and to in The of interaction was by the in and by shown in the Daxx and failed to with GR. In contrast, the mutant with a deletion of of Daxx was still of interacting with the of interaction with GR was that from the results were also with the these results that the C-terminal region of Daxx is and for its interaction with GR. the between interaction and GR transcriptional repression by Daxx, these Daxx mutants were for their respective to GR in overexpression of Daxx, was of GR-mediated transcriptional both and failed to that the C-terminal region of Daxx is for Daxx-mediated GR Taken together, these findings provide direct evidence that the interaction between Daxx and GR well with Daxx function as a GR Recent studies that PML overexpression the transcriptional repression and a well with the of PML to Daxx to the PODs H. Leo C. Zhu J. Wu X. O'Neil J. Park E.J. Chen J.D. Mol. Cell. Biol. 2000; 20: 1784-1796Crossref PubMed Scopus (309) Google Scholar). In this we that PML be to relieve the Daxx transrepression on GR activity. this COS-1 were with PML expression with the expression constructs either Daxx or Daxx-(501–740) and for GR transactivation shown in overexpression of PML in a of transrepression elicited by both Daxx and Daxx-(501–740) on GR in a further whether this by PML with the recruitment of Daxx to the PODs, were COS-1 were with a of PML, HA-Daxx, and as and with the by immunofluorescence or was a and was through the nucleus a and By contrast, an suggesting that the C-terminal region of is for the nuclear co-expression of PML in a of and as by the to the PODs and the of was not by PML, the findings that PML fails to with Taken together, these findings suggest that the by PML is through its to Daxx to PODs. is of that the of GR was not PML overexpression with the notion that PML not directly bind to GR (11Doucas V. Tini M. Egan D.A. Evans R.M. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 2627-2632Crossref PubMed Scopus (155) Google Scholar). and further that the recruitment of Daxx by PML to PODs plays an important role in regulating GR transcriptional activity, a PML sumoylation-defective mutant was to the for its to recruit Daxx to the PODs and to reverse the transrepression elicited by Daxx on GR. co-expression of sumoylation-defective PML mutant failed to recruit Daxx from to PODs sumoylation-defective PML mutant, the wild-type PML, was to relieve the Daxx transrepression effect on GR that the Daxx-mediated GR transrepression and the recruitment of Daxx to PODs by PML are an further the effect by PML on the GR transrepression and the Daxx nuclear we COS-1 with As2O3 has been shown to the SUMO-1 modification of PML, which in the recruitment of PML and Daxx to the PODs (19Torii S. Egan D.A. Evans R.A. Reed J.C. EMBO J. 1999; 18: 6037-6049Crossref PubMed Scopus (236) Google Scholar, 21Li H. Leo C. Zhu J. Wu X. O'Neil J. Park E.J. Chen J.D. Mol. Cell. Biol. 2000; 20: 1784-1796Crossref PubMed Scopus (309) Google Scholar, F. Muller S. Pandolfi P.P. Dejean A. Oncogene. 2001; 20: 1-9Crossref PubMed Scopus (94) Google Scholar). shown in As2O3 treatment a of the of POD as by analysis of endogenous PML and This treatment also rendered the of endogenous Daxx from to the PODs, leading to the of Daxx with PML As2O3 treatment in an of the GR-mediated transcriptional activity Taken together, the results of and immunofluorescence studies that PML GR transcriptional activation by Daxx from to the the translocation of Daxx to PODs and the GR-mediated COS-1 were with As2O3 for and immunofluorescence of endogenous Daxx and PML was The was as in A. COS-1 were with the MMTV-Luc reporter and GR expression the were with for and in with or As2O3 for activity was as described In the present we have identified Daxx as a protein and demonstrated that Daxx the GR transcriptional activation on We biochemical evidence that Daxx with GR in in and in mammalian cells. The interaction between GR and Daxx is through the C-terminal region of Furthermore, co-expression of PML the transcriptional repression by Daxx, correlating well with the recruitment of Daxx from the to the PODs. Our findings not provide the first direct link between Daxx expression and GR activity but also some light on the mechanism underlying the role of PML in regulating GR transcriptional Daxx was identified as the between receptor and N-terminal in X. R. Chang D. Cell. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). evidence that Daxx might function as a transcriptional through its interaction with a of transcription Daxx has been shown to the activity by a promoter through (19Torii S. Egan D.A. Evans R.A. Reed J.C. EMBO J. 1999; 18: 6037-6049Crossref PubMed Scopus (236) Google H. Leo C. Zhu J. Wu X. O'Neil J. Park E.J. Chen J.D. Mol. Cell. Biol. 2000; 20: 1784-1796Crossref PubMed Scopus (309) Google Scholar, D.Y. Shih H.M. J. Biol. Chem. 2002; 277: 25446-25456Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar). Daxx was also reported to the activity of the transcriptional Pax3 and ETS1 (22Hollenbach A.D. Sublett J.E. McPherson C.J. Grosveld G. EMBO J. 1999; 18: 3702-3711Crossref PubMed Scopus (185) Google Scholar, 23Li R. Pei H. Watson D.K. Papas T.S. Oncogene. 2000; 19: 745-753Crossref PubMed Scopus (161) Google Scholar). Daxx overexpression the endogenous Pax5 transcriptional activity in the and the murine Daxx potentiated Pax5 transcriptional activity in and murine (24Emelyanov A.V. Kovac C.R. Sepulveda M.A. Birshtein B.K. J. Biol. Chem. 2002; 277: 11156-11164Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). In the present study, we further demonstrated that Daxx could the GR-mediated transcriptional activation of The effect of Daxx on GR activity has also been demonstrated in several that this repressive effect is not a Furthermore, we also biochemical and evidence that the C-terminal region of Daxx is and to with GR and GR transcriptional activity. this C-terminal region of Daxx has also been reported to with other transcription as and ETS1 (19Torii S. Egan D.A. Evans R.A. Reed J.C. EMBO J. 1999; 18: 6037-6049Crossref PubMed Scopus (236) Google Scholar, 23Li R. Pei H. Watson D.K. Papas T.S. Oncogene. 2000; 19: 745-753Crossref PubMed Scopus (161) Google Scholar, A.V. Kovac C.R. Sepulveda M.A. Birshtein B.K. J. Biol. Chem. 2002; 277: 11156-11164Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar) as well as a of including PML, protein DNA and SUMO-1 H. Leo C. Zhu J. Wu X. O'Neil J. Park E.J. Chen J.D. Mol. Cell. Biol. 2000; 20: 1784-1796Crossref PubMed Scopus (309) Google Scholar, X. R. Chang D. Cell. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar, J. N. Y. Acad. Sci. 2000; PubMed Scopus Google Scholar, D. F. C. P. 1999; PubMed Scopus Google Scholar, J. Cell Sci. 1998; PubMed Google Scholar, S. D. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar, S.W. Biochem. 2000; PubMed Scopus Google Scholar). the C-terminal region of Daxx acts as a domain for protein-protein interactions. it is not demonstrated this domain a binding for these proteins with we that Daxx is involved in the through binding by factors to the located the C-terminal domain of Although Daxx as a transcriptional the mechanism as to it the transcriptional activation remains showed that the treatment with a deacetylase the repressive effect of Daxx H. Leo C. Zhu J. Wu X. O'Neil J. Park E.J. Chen J.D. Mol. Cell. Biol. 2000; 20: 1784-1796Crossref PubMed Scopus (309) Google Scholar), suggesting that histone may be involved in Daxx-mediated transcriptional interaction between the Daxx and has been demonstrated by in vitro and in vivo overexpression H. Leo C. Zhu J. Wu X. O'Neil J. Park E.J. Chen J.D. Mol. Cell. Biol. 2000; 20: 1784-1796Crossref PubMed Scopus (309) Google Scholar). Furthermore, al. has recently shown that endogenous from has an of and with proteins that are for transcriptional as histone deacetylase of chromatin as core histone and and a protein A.D. McPherson C.J. E.J. R. Grosveld G. J. Cell Sci. 2002; PubMed Google Scholar). The findings of the association with histone deacetylase are with notion that play an role in Daxx-mediated transcriptional via chromatin remodeling that Daxx was reported to be associated with chromatin in the PML A.M. Sotnikov A.G. Negorev D. Vladimirova O.V. Neff N. Kamitani T. Yeh E.T. Strauss III, J.F. Maul G.G. J. Cell Biol. 1999; 147: 221-234Crossref PubMed Scopus (694) Google Scholar) also the role of Daxx in the and/or of a chromatin Whether Daxx results in the chromatin of remains to be explored. of the present is to the mechanism as to PML GR transcriptional activity. PML has been proposed to function as a transcription cofactor through co-activators K.L. Mol. Cell. Biol. 2002; 22: 5259-5269Crossref PubMed Scopus (263) Google Scholar, T. Tini M. Evans R.M. Oncogene. 2001; 20: PubMed Scopus Google Scholar). For PML has been shown to the transactivation activity of and receptor A. J.F. F. The H. Mol. Endocrinol. 9: Google S. T. Chang F. Oncogene. 1998; PubMed Scopus Google Scholar). studies revealed that PML not directly with either or receptor but transcriptional as CBP and (11Doucas V. Tini M. Egan D.A. Evans R.M. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 2627-2632Crossref PubMed Scopus (155) Google Scholar, S. T. Chang F. Oncogene. 1998; PubMed Scopus Google Scholar, S. C. C. D. H. S. Pandolfi P.P. 1999; 23: PubMed Scopus Google Scholar). PML binds to CBP in CBP to PODs, and transcriptional activity of nuclear receptors as GR and receptor in (11Doucas V. Tini M. Egan D.A. Evans R.M. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 2627-2632Crossref PubMed Scopus (155) Google Scholar). a co-activator complex, of PML, and CBP, is recruited to suggesting that PML is a co-activator for receptors S. C. C. D. H. S. Pandolfi P.P. 1999; 23: PubMed Scopus Google Scholar). In this study, we an regulatory for PML in modulating GR transactivation function. The recruitment of Daxx to PODs by PML may mechanism the activity of the GR is Our results demonstrated that wild-type but not sumoylation-defective PML is for transrepression effect of Daxx on GR by Daxx to the PODs. that GR transcriptional activation a mechanism by modulating Daxx These findings are with the notion from studies that SUMO-1 modification of PML is for both the sequestration of Daxx to the PODs and of Daxx-mediated may that of Daxx into PODs through PML overexpression the access of Daxx to its repressive Lehembreet al. have recently reported that SUMO-1-modified PML could Pax3 transcriptional activity through sequestration of the Daxx into the PODs (26Lehembre F. Muller S. Pandolfi P.P. Dejean A. Oncogene. 2001; 20: 1-9Crossref PubMed Scopus (94) Google Scholar). Taken together, these findings suggest that PML may modulate the of a of transcription factors by altering the compartmentalization of its respective to the PODs. to this we have recently identified that nucleolar protein MSP58 the transactivation potential by sequestering Daxx to the nucleolus (25Lin D.Y. Shih H.M. J. Biol. Chem. 2002; 277: 25446-25456Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar). In light of these PODs and/or nucleolus may to the transcriptional activation of target by as Daxx, from the nuclear where transcription