A Novel Transcription Regulatory Complex Containing Death Domain-associated Protein and the ATR-X Syndrome Protein

Abstract

Death domain-associated protein (Daxx) is a multi-functional protein that modulates both apoptosis and transcription. Within the nucleus, Daxx is a component of the promyelocytic leukemia protein (PML) nuclear bodies (NBs) and interacts with a number of transcription factors, yet its precise role in transcription remains elusive. To further define the function of Daxx, we have isolated its interacting proteins in the nucleus using epitope-tagged affinity purification and identified X-linked mental retardation and α-thalassaemia syndrome protein (ATRX), a putative member of the SNF2 family of ATP-dependent chromatin remodeling proteins that is mutated in several X-linked mental retardation disorders. We show that substantial amounts of endogenous Daxx and ATRX exist in a nuclear complex. Daxx binds to ATRX through its paired amphipathic alpha helices domains. ATRX has ATPase activity that is stimulated by mononucleosomes, and patient mutations in the ATPase domain attenuate this activity. ATRX strongly represses transcription when tethered to a promoter. Daxx does not affect the ATPase activity of ATRX, however, it alleviates its transcription repression activity. In addition, ATRX is found in the PML-NBs, and this localization is mediated by Daxx. These results show that the ATRX·Daxx complex is a novel ATP-dependent chromatin-remodeling complex, with ATRX being the core ATPase subunit and Daxx being the targeting subunit. Moreover, the localization of ATRX to the PML-NBs supports the notion that these structures may play an important role in transcription regulation. Death domain-associated protein (Daxx) is a multi-functional protein that modulates both apoptosis and transcription. Within the nucleus, Daxx is a component of the promyelocytic leukemia protein (PML) nuclear bodies (NBs) and interacts with a number of transcription factors, yet its precise role in transcription remains elusive. To further define the function of Daxx, we have isolated its interacting proteins in the nucleus using epitope-tagged affinity purification and identified X-linked mental retardation and α-thalassaemia syndrome protein (ATRX), a putative member of the SNF2 family of ATP-dependent chromatin remodeling proteins that is mutated in several X-linked mental retardation disorders. We show that substantial amounts of endogenous Daxx and ATRX exist in a nuclear complex. Daxx binds to ATRX through its paired amphipathic alpha helices domains. ATRX has ATPase activity that is stimulated by mononucleosomes, and patient mutations in the ATPase domain attenuate this activity. ATRX strongly represses transcription when tethered to a promoter. Daxx does not affect the ATPase activity of ATRX, however, it alleviates its transcription repression activity. In addition, ATRX is found in the PML-NBs, and this localization is mediated by Daxx. These results show that the ATRX·Daxx complex is a novel ATP-dependent chromatin-remodeling complex, with ATRX being the core ATPase subunit and Daxx being the targeting subunit. Moreover, the localization of ATRX to the PML-NBs supports the notion that these structures may play an important role in transcription regulation. Daxx 1The abbreviations used are: Daxx, death-domain associated protein; ATRX, X-linked mental retardation and α-thalassaemia syndrome protein; GFP, green fluorescent protein; HA, hemagglutinin; PAH, paired amphipathic helix domain; PHD, plant homeodomain; PML, promyelocytic leukemia protein; PML-NBs, PML nuclear bodies; CMV, cytomegalovirus. was initially identified as a pro-apoptotic molecule that binds to the intracellular tail of the death receptor CD95 (Fas/Apo-1) and enhances apoptosis through the induction of the c-Jun NH2-terminal kinase (JNK) pathway (1Yang X. Khosravi-Far R. Chang H.Y. Baltimore D. Cell. 1997; 89: 1067-1076Abstract Full Text Full Text PDF PubMed Scopus (826) Google Scholar). Daxx associates with apoptosis signal-regulating kinase 1, an apical kinase of the JNK pathway, causing it to become active (2Chang H.Y. Nishitoh H. Yang X. Ichijo H. Baltimore D. Science. 1998; 281: 1860-1863Crossref PubMed Scopus (532) Google Scholar). Subsequent studies have revealed a role for Daxx in apoptosis induced by other stimuli, including transforming growth factor-β and interferons (3Perlman R. Schiemann W.P. Brooks M.W. Lodish H.F. Weinberg R.A. Nat. Cell Biol. 2001; 3: 708-714Crossref PubMed Scopus (301) Google Scholar, 4Gongora R. Stephan R.P. Zhang Z. Cooper M.D. Immunity. 2001; 14: 727-737Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar). Despite these cytoplasmic interactions, Daxx is mainly found in the nucleus, and its cytosolic translocation appears to be regulated. For example, the translocation of Daxx to the cytoplasm can be induced by CD95 engagement in a heat shock protein 27-inhibitable manner (5Charette S.J. Landry J. Ann. N. Y. Acad. Sci. 2000; 926: 126-131Crossref PubMed Scopus (126) Google Scholar). In addition, ASK1 can enhance the cytosolic localization of Daxx (6Ko Y.G. Kang Y.S. Park H. Seol W. Kim J. Kim T. Park H.S. Choi E.J. Kim S. J. Biol. Chem. 2001; 276: 39103-39106Abstract Full Text Full Text PDF PubMed Scopus (106) Google Scholar). On the contrary, accumulation of Daxx in the nucleus is observed during the activation of splenocytes (7Zhong S. Salomoni P. Ronchetti S. Guo A. Ruggero D. Pandolfi P.P. J. Exp. Med. 2000; 191: 631-640Crossref PubMed Scopus (193) Google Scholar). In the nucleus, Daxx is found in the promyelocytic leukemia protein nuclear bodies (PML-NBs) (8Torii S. Egan D.A. Evans R.A. Reed J.C. EMBO J. 1999; 18: 6037-6049Crossref PubMed Scopus (235) Google Scholar, 9Ishov A.M. Sotnikov A.G. Negorev D. Vladimirova O.V. Neff N. Kamitani T. Yeh E.T. Strauss 3rd, J.F. Maul G.G. J. Cell Biol. 1999; 147: 221-234Crossref PubMed Scopus (677) Google Scholar, 10Everett R.D. Earnshaw W.C. Pluta A.F. Sternsdorf T. Ainsztein A.M. Carmena M. Ruchaud S. Hsu W.L. Orr A. J. Cell Sci. 1999; 112: 3443-3454Crossref PubMed Google Scholar), macromolecular complexes that regulate a wide range of cellular processes (11Borden K.L. Mol. Cell. Biol. 2002; 22: 5259-5269Crossref PubMed Scopus (263) Google Scholar, 12Salomoni P. Pandolfi P.P. Cell. 2002; 108: 165-170Abstract Full Text Full Text PDF PubMed Scopus (466) Google Scholar). The PML-NBs are dispersed in over 95% of cases of acute promyelocytic leukemia (APL) by the PML-retinoid acid receptor fusion protein generated by a t(15,17) translocation. Treatment of APL patients with all-trans-retinoid acid or arsenic oxide induces degradation of the fusion protein, restoration of normal PML-NB appearance, and concomitant remission of the disease, implicating a critical function of the PML-NBs in protecting against APL pathogenesis (11Borden K.L. Mol. Cell. Biol. 2002; 22: 5259-5269Crossref PubMed Scopus (263) Google Scholar, 12Salomoni P. Pandolfi P.P. Cell. 2002; 108: 165-170Abstract Full Text Full Text PDF PubMed Scopus (466) Google Scholar, 13Melnick A. Licht J.D. Blood. 1999; 93: 3167-3215Crossref PubMed Google Scholar). In addition, the PML-NBs are disrupted by various viral proteins and increase in both size and number in response to anti-viral cytokine interferons that up-regulate PML-NB components, suggesting a role for the PML-NBs in anti-viral responses (14Regad T. Chelbi-Alix M.K. Oncogene. 2001; 20: 7274-7286Crossref PubMed Scopus (242) Google Scholar). Furthermore, cells deficient in PML are resistant to a wide range of apoptotic stimuli, including UV radiation and engagement of CD95 (15Wang Z.G. Ruggero D. Ronchetti S. Zhong S. Gaboli M. Rivi R. Pandolfi P.P. Nat. Genet. 1998; 20: 266-272Crossref PubMed Scopus (100) Google Scholar), and Daxx appears to be able to regulate apoptosis from the PML-NBs (7Zhong S. Salomoni P. Ronchetti S. Guo A. Ruggero D. Pandolfi P.P. J. Exp. Med. 2000; 191: 631-640Crossref PubMed Scopus (193) Google Scholar, 8Torii S. Egan D.A. Evans R.A. Reed J.C. EMBO J. 1999; 18: 6037-6049Crossref PubMed Scopus (235) Google Scholar). How the PML-NBs function in tumor suppression, anti-viral responses, and apoptosis is not well defined. Several cellular proteins have been found in the PMLNBs in addition to PML and Daxx, including p53, pRb, Sp100, SUMO (small ubiquitin-like modifier), CBP, HAUSP, and BLM, and a role for the PML-NBs in transcription has been proposed (16Zhong S. Salomoni P. Pandolfi P.P. Nat. Cell Biol. 2000; 2: E85-E90Crossref PubMed Scopus (490) Google Scholar). However, a better understanding of PML-NB function requires the identification of additional key components that associate with these structures. Daxx has been shown to be a transcription regulatory protein and to associate with several sequence-specific transcription factors, such as Pax3, Pax5, ETS1, and the glucocorticoid receptor (17Hollenbach A.D. Sublett J.E. McPherson C.J. Grosveld G. EMBO J. 1999; 18: 3702-3711Crossref PubMed Scopus (185) Google Scholar, 18Li 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 (307) Google Scholar, 19Li R. Pei H. Watson D.K. Papas T.S. Oncogene. 2000; 19: 745-753Crossref PubMed Scopus (158) Google Scholar, 20Emelyanov 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 (96) Google Scholar, 21Lin D.Y. Lai M.Z. Ann D.K. Shih H.M. J. Biol. Chem. 2003; 278: 15958-15965Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar). The mechanism by which Daxx regulates transcription is not well understood, but it is conceivable that Daxx may associate with chromatin-remodeling complexes. Indeed, the association of Daxx with histone deacetylase chromatin remodeling complexes has been reported (18Li 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 (307) Google Scholar, 22Hollenbach A.D. McPherson C.J. Mientjes E.J. Iyengar R. Grosveld G. J. Cell Sci. 2002; 115: 3319-3330Crossref PubMed Google Scholar). It remains to be determined whether Daxx also engages the other major class of chromatin remodeling molecules, the ATP-dependent remodeling complexes. To further define the function of Daxx, we have devised a convenient affinity purification strategy to isolate Daxx-associated proteins. Here, we describe the identification and characterization of ATRX as a Daxx-interacting protein. ATRX is a large protein of ∼280 kDa that contains a putative ATPase/helicase domain homologous to that found in members of the SNF2 family of chromatin-remodeling proteins. In addition, it also contains a plant homeodomain (PHD) zinc finger domain, which is to the family of proteins. in the X-linked ATRX are the putative ATPase/helicase domain and the causing a mental retardation syndrome that is associated with and α-thalassaemia Cell. Full Text PDF PubMed Scopus Google Scholar, S. Mol. Genet. PubMed Scopus Google Scholar, S. S. J. N. A. M. G. Nat. Genet. 1997; PubMed Scopus Google Scholar). Despite its to chromatin-remodeling the precise function of ATRX remains We show that endogenous Daxx and ATRX are in a nuclear complex. Daxx interacts with ATRX through its NH2-terminal paired amphipathic alpha helices domains. In addition, we that ATRX ATPase and patient mutations attenuate this activity. Furthermore, we that ATRX is to the Daxx ATRX to the PML-NBs and transcription regulation. These results that the ATRX·Daxx complex is a novel chromatin remodeling complex and that Daxx may regulate ATRX activity by its cellular The localization of ATRX to the PML-NBs also supports the notion that the PML-NBs regulate cellular processes by transcription. from the against and and affinity and and protein and and protein and The was Mol. Genet. 2000; PubMed Scopus Google Scholar). in Daxx protein and the of Daxx and ATRX to an NH2-terminal in X. Chang H.Y. Baltimore D. Science. 1998; 281: PubMed Scopus Google Scholar). the domain of and a fusion of the domain of ATRX, also in The fusion in the or was in For in ATRX and proteins and with a or an NH2-terminal and The ATRX mutations using the to the and by The mutations PHD, the in the zinc finger domain; and the and mutations in the putative ATPase/helicase domain which have been Cell. Full Text PDF PubMed Scopus Google a in the of nuclear cells from from the Cell in of and further disrupted by and the by for The in and the was with a to nuclear To protein in or the was cells in with of by the cells with and with of X. Chang H.Y. Baltimore D. Science. 1998; 281: PubMed Scopus Google Scholar). Cell with for the with of nuclear The with and with The proteins with of for The proteins of proteins was and Daxx-associated proteins by and of nuclear a by an protein in various with acid and by and To the endogenous ATRX and Daxx, cells in Cell with the by with protein The proteins to and To the domain Daxx, Daxx and various Daxx proteins in The with and endogenous ATRX protein to the was by various ATRX in and to associate with endogenous Daxx was by and of ATRX, and with viral cells to to the several of the was used to the cells and proteins as with Mol. Cell. Biol. 2002; 22: PubMed Scopus Google Scholar). The was in of and with or and in a purification The was for The proteins in the using protein or or with and the proteins with or or with The protein was in in and ATPase ATPase of ATRX, and as with T. Wu C. Cell. Full Text PDF PubMed Scopus Google Scholar). proteins with of or of in a of of ATPase and The was for by of of the was by with a in and The of to was by or cells in cells with for was by the with for and with for for with or as by with or a cells in and the by the with of Y. R. H. P. M. D. Mol. Cell. 1998; Full Text Full Text PDF PubMed Scopus (242) Google Scholar), of and various amounts of and Daxx. The of was by the cells and for activity with a to the the of the of the shown are of in of ATRX as a Daxx-interacting Daxx-associated we a Daxx protein in cells and the protein using The was with a large of nuclear to its interacting proteins. has major the protein is in cells and is to have the it the of shown in a protein kDa in size in the nuclear associated with the but not the protein was by and of which the of ATRX To the in as well as the the endogenous we using of Daxx was and ATRX was by in the but not in with an Daxx was in the These also revealed that a of endogenous Daxx and ATRX are in the complex not To further the complex, we nuclear using a and from the by with and The Daxx and ATRX proteins in a complex of suggesting a of Daxx and ATRX in the complex. ATRX was shown to be in a complex that including Daxx Y. R. Z. Yang D. S. J. S. D. W. Acad. Sci. S. A. 2003; PubMed Scopus Google Scholar). The we observed are to the of the complex to used for Daxx with ATRX its NH2-terminal the of Daxx that its with ATRX, we various of Daxx, with an NH2-terminal The proteins in cells and with and the of endogenous ATRX in the was by shown in Daxx that the NH2-terminal including the paired amphipathic helix able to associate with ATRX the was the domain was also In of the mutations that the domain to to ATRX these results that the NH2-terminal of Daxx its with this is the of a function for the as of the Daxx-interacting proteins reported in the associate with the of Daxx (1Yang X. Khosravi-Far R. Chang H.Y. Baltimore D. Cell. 1997; 89: 1067-1076Abstract Full Text Full Text PDF PubMed Scopus (826) Google Scholar, R. Schiemann W.P. Brooks M.W. Lodish H.F. Weinberg R.A. Nat. Cell Biol. 2001; 3: 708-714Crossref PubMed Scopus (301) Google Scholar, A.D. Sublett J.E. McPherson C.J. Grosveld G. EMBO J. 1999; 18: 3702-3711Crossref PubMed Scopus (185) Google Scholar, 18Li 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 (307) Google Scholar, 19Li R. Pei H. Watson D.K. Papas T.S. Oncogene. 2000; 19: 745-753Crossref PubMed Scopus (158) Google Scholar, 20Emelyanov 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 (96) Google Scholar, 21Lin D.Y. Lai M.Z. Ann D.K. Shih H.M. J. Biol. Chem. 2003; 278: 15958-15965Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar). the Daxx-interacting of the Daxx-interacting domain of ATRX, we generated various ATRX that both of the ATRX protein can with Daxx, that ATRX may Daxx-interacting and revealed that of the ATRX well with Daxx, the of ATRX that these to a Daxx-interacting In addition, the and may a Daxx-interacting domain and However, the domain to Daxx strongly the and may be the domain mainly for the ATRX·Daxx and In identified of ATRX, the NH2-terminal domain and the ATPase/helicase are not for the with Daxx ATRX ATPase by ATPase/helicase domain of ATRX with found in members of the SNF2 family of chromatin-remodeling proteins. We to whether the ATRX protein ATPase activity. We ATRX for and cells using The ATRX protein was by an affinity and by by and with or and the and proteins an NH2-terminal and to by affinity shown in ATRX in a manner To the of the we the ATPase of the proteins from and found that the of ATRX to the of protein, was that of but the ATPase activity of It is that the observed ATPase activity from the ATRX protein as to or proteins in the the activity was or when ATRX mutations studies have shown that the ATPase activity of both the and the of chromatin remodeling is stimulated by However, the responses of these to and are proteins are stimulated well by both of proteins are stimulated by H.Y. Cell. 2002; 108: Full Text Full Text PDF PubMed Scopus Google Scholar). To the of these the ATPase activity of ATRX, we whether or the ATPase activity of The ATPase activity of ATRX in response to but was not stimulated by The of the mononucleosomes, was In addition, the response of ATRX was the activity of the ATRX·Daxx complex, which be stimulated well by both and chromatin Y. R. Z. Yang D. S. J. S. D. W. Acad. Sci. S. A. 2003; PubMed Scopus Google Scholar). a we the ATPase activity of the proteins in the of or and observed that it was with with the ATPase activity of being stimulated by both and the ATPase activity of being by H.Y. Cell. 2002; 108: Full Text Full Text PDF PubMed Scopus Google Scholar). the ATRX ATPase syndrome is associated with a of mutations in the ATRX suggesting that the mechanism is the of ATRX protein However, the of mutations in the ATPase domain that such to this domain be patient mutations may attenuate activity it To whether mutations or attenuate ATPase we generated ATRX proteins mutations the ATPase domain and an and as a the the domain proteins in and to ATPase activity. the in the domain ATPase mutations in the ATPase domain activity the in the the ATPase activity These results that patient mutations the ATPase domain attenuate activity and that this domain is critical for ATRX Moreover, it that mutations in other of the protein not ATPase activity but ATRX function through and that ATPase activity is The ATPase of ATRX by shown that ATRX has ATPase activity that is in we whether Daxx regulates the ATPase activity of Daxx and the the ATRX interacting domain, in cells and to these Daxx proteins to the ATPase was observed and Daxx does not to the ATPase activity of ATRX to and by the of Daxx regulation. ATRX is a chromatin-remodeling we that ATRX to a affect transcription. We ATRX to the domain and this fusion cells with a of the kinase promoter. strongly of the and transcription repression was the targeting of ATRX to the ATRX to ATRX can function as a transcription is with that ATP-dependent chromatin-remodeling can the of the of W. 2002; PubMed Scopus Google Scholar). Daxx was in this transcription repression by ATRX was in a Daxx manner and Daxx the function of ATRX in transcription regulation. of ATRX to the Daxx the ATPase activity of ATRX but we the that Daxx the cellular localization of that Daxx is found in the PML-NBs, we whether ATRX is also to these nuclear bodies whether this localization is Daxx. ATRX in cells a with several nuclear that with an In addition, with the size of the PML-NBs was and ATRX was found to be in the PML-NBs These results that ATRX is a PML-NB Daxx ATRX to the the role of Daxx in the targeting of ATRX to the PML-NBs, we whether Daxx enhances the PML-NB localization of of a fusion of ATRX in cells a of nuclear against a nuclear that was to the endogenous protein. The with Daxx in the PML-NBs this localization was when Daxx was with To PML-NB targeting of Daxx, we PML in the as studies have shown that PML Daxx to the nuclear bodies (7Zhong S. Salomoni P. Ronchetti S. Guo A. Ruggero D. Pandolfi P.P. J. Exp. Med. 2000; 191: 631-640Crossref PubMed Scopus (193) Google Scholar, 9Ishov A.M. Sotnikov A.G. Negorev D. Vladimirova O.V. Neff N. Kamitani T. Yeh E.T. Strauss 3rd, J.F. Maul G.G. J. Cell Biol. 1999; 147: 221-234Crossref PubMed Scopus (677) Google Scholar, 18Li 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 (307) Google Scholar). We the of ATRX that its PML-NB ATRX used for the to these in of including of the Daxx-interacting domain, a in the nucleus However, ATRX and in nuclear structures these which the Daxx-interacting domain not to the PML-NBs when with PML and Daxx and not the ATRX the Daxx-interacting and to the PML-NBs when with Daxx and PML In the the Daxx-interacting domain not to the nuclear bodies in the of Daxx and PML and not The the to to Daxx and the PML-NB localization of the ATRX that Daxx ATRX to the nuclear we with Daxx or with a Daxx the NH2-terminal domain or the The of Daxx, but not of the was with accumulation in the these results show that Daxx ATRX to the PML-NBs through its to to both PML and Daxx was identified as a of apoptosis through JNK Subsequent studies have shown that it is also a key component of the PML nuclear bodies and that it regulates transcription through its with various proteins. In the we that Daxx interacts with ATRX, as to the role of Daxx in regulation. has shown that ATRX is a member of the SNF2 family of ATP-dependent chromatin remodeling proteins Cell. Full Text PDF PubMed Scopus Google Scholar, S. Mol. Genet. PubMed Scopus Google Scholar). we that ATRX has ATPase activity in the of ATRX, is to other chromatin remodeling proteins. In addition, Y. R. Z. Yang D. S. J. S. D. W. Acad. Sci. S. A. 2003; PubMed Scopus Google that an ATRX·Daxx complex to have ATP-dependent remodeling activity from that of other protein complexes in that it may function the of the ATPase domain of ATRX is a of patient mutations the in this domain of the suggesting that mutations in may be Cell. Full Text PDF PubMed Scopus Google Scholar). with this we that patient mutations and ATRX ATPase a in the In a in the domain normal ATPase suggesting that mutations in this domain have ATPase activity but ATRX function by studies have that chromatin-remodeling can the of and the of we found that ATRX, when tethered to strongly transcription by the of the kinase with this is the localization of ATRX to and its with both further a role for Moreover, with to the we that the chromatin remodeling activity of ATRX is for transcription Daxx does not affect the ATPase activity of it appears to regulate the cellular localization of We that Daxx can ATRX to the PML-NBs, it may ATRX activity by ATRX from its It remains to be determined whether Daxx also ATRX to sequence-specific transcription is Daxx interacts with ATRX through its NH2-terminal but with sequence-specific transcription factors, such as Pax3, Pax5, ETS1, and the glucocorticoid through its (17Hollenbach A.D. Sublett J.E. McPherson C.J. Grosveld G. EMBO J. 1999; 18: 3702-3711Crossref PubMed Scopus (185) Google Scholar, 18Li 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 (307) Google Scholar, 19Li R. Pei H. Watson D.K. Papas T.S. Oncogene. 2000; 19: 745-753Crossref PubMed Scopus (158) Google Scholar, 20Emelyanov 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 (96) Google Scholar, 21Lin D.Y. Lai M.Z. Ann D.K. Shih H.M. J. Biol. Chem. 2003; 278: 15958-15965Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar). Daxx may function as a proteins and chromatin remodeling complexes and the of transcription regulatory complexes. The PML-NBs regulate a wide range of cellular including tumor and growth suppression, anti-viral responses, and cellular (11Borden K.L. Mol. Cell. Biol. 2002; 22: 5259-5269Crossref PubMed Scopus (263) Google Scholar, 12Salomoni P. Pandolfi P.P. Cell. 2002; 108: 165-170Abstract Full Text Full Text PDF PubMed Scopus (466) Google Scholar). The of the PML-NBs, however, are not well defined. a role for the PML-NBs in (16Zhong S. Salomoni P. Pandolfi P.P. Nat. Cell Biol. 2000; 2: E85-E90Crossref PubMed Scopus (490) Google Scholar). Several transcription regulatory proteins have been found in the PML-NBs, including transcription such as and as well as CBP, a member of the histone protein The identification of ATRX, a chromatin-remodeling protein, the PML-NBs the notion that these nuclear structures may be critical for the of transcription. It is conceivable that the PML-NBs may regulate activity by the of regulatory proteins to it may the of regulatory complexes by the complex components of The function of an ATRX·Daxx complex can be this However, we that both proteins are for normal in ATRX to a mental retardation deficient in Daxx are It is that the ATRX·Daxx complex regulates the transcription of important of such a function the identification of We J. for and the Cell for We also R. J. for and for the C. for A. and G. Maul for PML-NB and members of the and Yang for was by the of the and the of