Enhancer of Polycomb1 Acts on Serum Response Factor to Regulate Skeletal Muscle Differentiation

Abstract

Skeletal muscle differentiation is well regulated by a series of transcription factors. We reported previously that enhancer of polycomb1 (Epc1), a chromatin protein, can modulate skeletal muscle differentiation, although the mechanisms of this action have yet to be defined. Here we report that Epc1 recruits both serum response factor (SRF) and p300 to induce skeletal muscle differentiation. Epc1 interacted physically with SRF. Transfection of Epc1 to myoblast cells potentiated the SRF-induced expression of skeletal muscle-specific genes as well as multinucleation. Proximal CArG box in the skeletal α-actin promoter was responsible for the synergistic activation of the promoter-luciferase. Epc1 knockdown caused a decrease in the acetylation of histones associated with serum response element (SRE) of the skeletal α-actin promoter. The Epc1·SRF complex bound to the SRE, and the knockdown of Epc1 resulted in a decrease in SRF binding to the skeletal α-actin promoter. Epc1 recruited histone acetyltransferase activity, which was potentiated by cotransfection with p300 but abolished by si-p300. Epc1 directly bound to p300 in myoblast cells. Epc1+/− mice showed distortion of skeletal α-actin, and the isolated myoblasts from the mice had impaired muscle differentiation. These results suggest that Epc1 is required for skeletal muscle differentiation by recruiting both SRF and p300 to the SRE of muscle-specific gene promoters. Skeletal muscle differentiation is well regulated by a series of transcription factors. We reported previously that enhancer of polycomb1 (Epc1), a chromatin protein, can modulate skeletal muscle differentiation, although the mechanisms of this action have yet to be defined. Here we report that Epc1 recruits both serum response factor (SRF) and p300 to induce skeletal muscle differentiation. Epc1 interacted physically with SRF. Transfection of Epc1 to myoblast cells potentiated the SRF-induced expression of skeletal muscle-specific genes as well as multinucleation. Proximal CArG box in the skeletal α-actin promoter was responsible for the synergistic activation of the promoter-luciferase. Epc1 knockdown caused a decrease in the acetylation of histones associated with serum response element (SRE) of the skeletal α-actin promoter. The Epc1·SRF complex bound to the SRE, and the knockdown of Epc1 resulted in a decrease in SRF binding to the skeletal α-actin promoter. Epc1 recruited histone acetyltransferase activity, which was potentiated by cotransfection with p300 but abolished by si-p300. Epc1 directly bound to p300 in myoblast cells. Epc1+/− mice showed distortion of skeletal α-actin, and the isolated myoblasts from the mice had impaired muscle differentiation. These results suggest that Epc1 is required for skeletal muscle differentiation by recruiting both SRF and p300 to the SRE of muscle-specific gene promoters. Skeletal muscle development requires a series of precisely orchestrated steps after mesodermal precursor cells are committed to the skeletal muscle lineage (1Li S. Czubryt M.P. McAnally J. Bassel-Duby R. Richardson J.A. Wiebel F.F. Nordheim A. Olson E.N. Proc. Natl. Acad. Sci. U. S. A. 2005; 102: 1082-1087Crossref PubMed Scopus (230) Google Scholar). Upon receiving the environmental signals, myoblasts can differentiate into muscles by withdrawing from the cell cycle and fusing with neighboring myoblasts to make multinucleated myotubes (2Edmondson D.G. Olson E.N. J. Biol. Chem. 1993; 268: 755-758Abstract Full Text PDF PubMed Google Scholar). During differentiation, hundreds of muscle-specific genes are transcriptionally activated, whereas the genes associated with cell proliferation are repressed (3McKinsey T.A. Zhang C.L. Olson E.N. Curr. Opin. Genet. Dev. 2001; 11: 497-504Crossref PubMed Scopus (352) Google Scholar). Myogenic fates are determined by essential transcription factors. These include the muscle regulatory factors (MRFs) 4The abbreviations used are: MRFmuscle regulatory factorSRFserum response factorRTreverse transcriptionHAhemagglutininGSTglutathione S-transferaseSREserum response element. of the basic helix-loop-helix family proteins, such as MyoD, Myf5, myogenin, and MRF4. Muscle differentiation depends on the interplay of these skeletal muscle-specific factors with the members of myocyte enhancer factor-2 (MEF2), a MADS box transcription factor (4Black B.L. Olson E.N. Annu. Rev. Cell Dev. Biol. 1998; 14: 167-196Crossref PubMed Scopus (853) Google Scholar). muscle regulatory factor serum response factor reverse transcription hemagglutinin glutathione S-transferase serum response element. Serum response factor (SRF) is an important transcription factor for cell survival and differentiation in diverse tissues (5Flück M. Booth F.W. Waxham M.N. Biochem. Biophys. Res. Commun. 2000; 270: 488-494Crossref PubMed Scopus (48) Google Scholar). Likewise, in skeletal muscle cells, it is well known that SRF is responsible for the transcriptional activation of muscle-specific genes (6Croissant J.D. Kim J.H. Eichele G. Goering L. Lough J. Prywes R. Schwartz R.J. Dev. Biol. 1996; 177: 250-264Crossref PubMed Scopus (157) Google Scholar). For example, SRF mRNA and nuclear SRF protein levels increase more than 40-fold when primary skeletal myoblasts are withdrawn from the cell cycle, which precedes the up-regulation of the muscle-specific proteins. However, the dominant-negative SRF mutant blocks the transcription of muscle-specific genes such as skeletal α-actin during myogenesis (6Croissant J.D. Kim J.H. Eichele G. Goering L. Lough J. Prywes R. Schwartz R.J. Dev. Biol. 1996; 177: 250-264Crossref PubMed Scopus (157) Google Scholar), which suggests that SRF is an important prerequisite for the initiation of muscle differentiation. Recently, we reported that enhancer of polycomb1 (Epc1) mediates skeletal muscle differentiation by interacting with homeodomain only protein (Hop or Hod) and that muscle regeneration is impaired in Hop null mice (7Kee H.J. Kim J.R. Nam K.I. Park H.Y. Shin S. Kim J.C. Shimono Y. Takahashi M. Jeong M.H. Kim N. Kim K.K. Kook H. J. Biol. Chem. 2007; 282: 7700-7709Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar). Epc1 was first described to enhance the phenotypes of homozygotic mutations of the polycomb group gene in Drosophila (8Stankunas K. Berger J. Ruse C. Sinclair D.A. Randazzo F. Brock H.W. Development. 1998; 125: 4055-4066Crossref PubMed Google Scholar). Previous reports elucidated that Epc1 may act as a transcription co-factor as a binding partner of other transcription factors such as E2F6 (9Attwooll C. Oddi S. Cartwright P. Prosperini E. Agger K. Steensgaard P. Wagener C. Sardet C. Moroni M.C. Helin K. J. Biol. Chem. 2005; 280: 1199-1208Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar) or RET finger protein (10Shimono Y. Murakami H. Hasegawa Y. Takahashi M. J. Biol. Chem. 2000; 275: 39411-39419Abstract Full Text Full Text PDF PubMed Scopus (85) Google Scholar). Although Epc1 is known to associate with other transcriptional modulators, the biological role of Epc1 and its regulatory mechanism in mammalian tissues remains to be described. In this study, we postulated that Epc1 induces muscle differentiation by interacting with SRF, an important modulator of muscle differentiation (11Weinhold B. Schratt G. Arsenian S. Berger J. Kamino K. Schwarz H. Rüther U. Nordheim A. EMBO J. 2000; 19: 5835-5844Crossref PubMed Scopus (75) Google Scholar). Thus, we studied the mechanism of action of Epc1 in association with SRF and p300 and also investigated the muscle phenotypes of mice in which Epc1 expression was disrupted. The Epc1-mediated enhancement of SRF-dependent muscle gene expression is mediated by its interaction with p300, which possesses histone acetyltransferase activity. Epc1 heterozygous mice show a delay in myoblast differentiation, which suggests that Epc1 is a novel modulator of skeletal muscle differentiation. pCMV-myc-mouse Epc1 was described previously. pCMX-p300 was kindly provided by Prof. Debabrata Chakravarti (Northwestern University, Chicago). pCGN-HA-SRF was kindly provided by Prof. Jonathan A. Epstein (University of Pennsylvania, Philadelphia). For the skeletal α-actin promoter-reporter assay, −450 to +26 base pairs from the transcription start site were amplified from mouse genomic DNA and subcloned into pGL3 basic vector (Promega, Madison, WI). The CArG-far (−419 to −410) and -near (−97 to −88) mutations of the skeletal α-actin promoter were generated by site-directed mutagenesis by using the QuikChange kit (Stratagene Inc., La Jolla, CA). si-p300 was purchased from Dharmacon Inc. (Chicago). All plasmids were confirmed by sequencing. Epc1 antibody was described previously (7Kee H.J. Kim J.R. Nam K.I. Park H.Y. Shin S. Kim J.C. Shimono Y. Takahashi M. Jeong M.H. Kim N. Kim K.K. Kook H. J. Biol. Chem. 2007; 282: 7700-7709Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar). Antibodies were used to recognize MyoD (C-20, Sc-304), myogenin (M-225, Sc-576), SRF (G-20, Sc-335), c-Myc (9E10, Sc-40), and p300 (c-20, Sc-585) (all of the above were from Santa Cruz Biotechnology (Santa Cruz, CA)); anti-acetyl-histone H3 (06–599), anti-acetyl-histone H4 (06–866), and anti-histone H3 (05–499) (from Upstate Biotechnology, Lake Placid, NY)); skeletal α-actin (catalogue No. 18-272-196320, Genway Biotech, Inc., San Diego); and anti-histone H4 (catalogue No. 2592, Cell Signaling Technology Inc., Danvers, MA). H9c2, COS-7, 293T, 10T1/2, and C2C12 cells were obtained from the Korean Cell Line Bank and were maintained with Dulbecco's modified Eagle's medium containing 10 or 15% fetal bovine serum for C2C12 cells. Antisense Epc1 cells were described previously (7Kee H.J. Kim J.R. Nam K.I. Park H.Y. Shin S. Kim J.C. Shimono Y. Takahashi M. Jeong M.H. Kim N. Kim K.K. Kook H. J. Biol. Chem. 2007; 282: 7700-7709Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar). For transient transfection of SRF and Epc1, pCGN-HA-SRF and/or pCMV-myc-Epc1 was introduced to 293T cells by use of FuGENE 6 transfection reagent (Roche Diagnostics) and to C2C12 or H9c2 cells by use of Lipofectamine Plus reagent (Invitrogen). Promoter analysis, immunoprecipitation, Western blot, fluorescent immunocytochemistry, and RT-PCR were described previously (7Kee H.J. Kim J.R. Nam K.I. Park H.Y. Shin S. Kim J.C. Shimono Y. Takahashi M. Jeong M.H. Kim N. Kim K.K. Kook H. J. Biol. Chem. 2007; 282: 7700-7709Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar). The antibodies for Western blot analysis were anti-HA (1:500), Epc1 (1:200), p300 (1:1000), and actin (1:2000). The primer sequences for the RT-PCR reaction will be provided upon request. RT-PCR amplification products were confirmed by sequencing. Chromatin immunoprecipitation assays were performed by using a commercially available assay kit according to the manufacturer's instructions (Upstate Biotechnology). Briefly, cells were treated with 1% formaldehyde for 10 min. The sonicated chromatin was immunoprecipitated with specific antibodies and then recovered with protein A-agarose/salmon sperm DNA beads. After reversing the cross-links, chromatin was subjected to proteinase K digestion, and the DNA was purified. A 197-bp fragment corresponding to nucleotides −192 to +5 of the rat skeletal α-actin promoter was amplified by PCR. Sequential chromatin immunoprecipitation was performed as described (12Bernstein B.E. Mikkelsen T.S. Xie X. Kamal M. Huebert D.J. Cuff J. Fry B. Meissner A. Wernig M. Plath K. Jaenisch R. Wagschal A. Feil R. Schreiber S.L. Lander E.S. Cell. 2006; 125: 315-326Abstract Full Text Full Text PDF PubMed Scopus (4068) Google Scholar). Epc1 precipitates were then eluted with standard elution buffer, except for with and the chromatin was recruited by acetyltransferase assays were performed as described previously P. S. A. Chakravarti Cell. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). After cells were with assay and immunoprecipitated with specific protein were of histones (Roche and were to the precipitates and for products were by and by use of a The was by the and cells were purchased from of after of the sequences by amplification of The gene vector was in the in the first of the mouse Epc1, and the gene was confirmed by Inc., The mouse cell were into and then into The mice were to to heterozygous Epc1 mice Inc., was by blot analysis or gene in the gene The mice were maintained by The of myoblasts was described previously (7Kee H.J. Kim J.R. Nam K.I. Park H.Y. Shin S. Kim J.C. Shimono Y. Takahashi M. Jeong M.H. Kim N. Kim K.K. Kook H. J. Biol. Chem. 2007; 282: 7700-7709Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar). and of muscles from Epc1 heterozygous or mice were as described previously (7Kee H.J. Kim J.R. Nam K.I. Park H.Y. Shin S. Kim J.C. Shimono Y. Takahashi M. Jeong M.H. Kim N. Kim K.K. Kook H. J. Biol. Chem. 2007; 282: 7700-7709Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar). Inc., was used for development in the Skeletal α-actin was with after with specific primary antibody and (Invitrogen). Epc1 to SRF, we first performed by pCMV-myc-Epc1 and SRF Epc1 in 293T cells. Epc1 also SRF of Epc1 and SRF were confirmed in C2C12 cells In association Epc1 and SRF was by a glutathione S-transferase in SRF was recruited by were in the of cells the biological of the interaction of Epc1 and SRF was we the of Epc1 in C2C12 cells. we described in the report using H9c2 cells (7Kee H.J. Kim J.R. Nam K.I. Park H.Y. Shin S. Kim J.C. Shimono Y. Takahashi M. Jeong M.H. Kim N. Kim K.K. Kook H. J. Biol. Chem. 2007; 282: 7700-7709Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar), Epc1 was in after serum MyoD is an important that induces muscle and differentiation B. Curr. Opin. Genet. Dev. 1998; PubMed Scopus Google Scholar). We the expression of MyoD after cotransfection of SRF and Epc1 the expression of MyoD by SRF A and Likewise, cotransfection of Epc1 and SRF the expression of myogenin and a of skeletal muscle differentiation and J. K. J. Biol. Chem. 2007; 282: Full Text Full Text PDF PubMed Scopus Google Scholar). The expression of SRF a increase in the of multinucleated cells. Although Epc1 induce it potentiated the myoblast differentiation We studied Epc1 the expression of the muscle-specific genes as well as transcription factors in C2C12 myoblast cells after transient transfection of pCGN-HA-SRF or SRF and Epc1 were as in The expression of skeletal α-actin, a primary of skeletal muscle J.A. Booth F.W. J. Cell 1998; 275: PubMed Google Scholar), was by transfection of SRF, which was potentiated by cotransfection of In myogenin expression was by transfection of both genes A and The levels of MyoD and of muscle-specific genes such as muscle E.S. J.D. PubMed Scopus Google Scholar) were also by of Epc1 and SRF and However, the levels of or which a CArG box in promoter G. M. M. P. N. A. Biol. Cell. 1998; PubMed Scopus Google Scholar), were by transfection of SRF and The in the of of muscle-specific genes were by after skeletal muscle-specific skeletal α-actin an SRE in the promoter J.A. Booth F.W. J. Muscle Res. Cell 1998; 19: PubMed Scopus Google Scholar). is responsible for the action of Epc1, we performed a transfection assay with the promoter of skeletal α-actin J. Res. 1998; PubMed Scopus Google Scholar), which CArG Transfection of SRF the promoter by the cotransfection of Epc1 potentiated the by which suggests that the synergistic activation is mediated by the transcriptional of the promoter The mouse skeletal α-actin promoter as and CArG-far J.A. Booth F.W. J. Muscle Res. Cell 1998; 19: PubMed Scopus Google Scholar). which CArG box is required for the synergistic action of SRF and Epc1, mutations were introduced into the or the CArG box Epc1 and SRF the skeletal with the CArG-far the was abolished by the or CArG mutations and Epc1 to the SRE with SRF, we performed chromatin immunoprecipitation assays with H9c2 cells. In with rat skeletal α-actin CArG box with a to the of mouse skeletal α-actin Epc1 antibody the DNA the SRE in the promoter whereas it to the containing the and and We SRF and Epc1 to the SRE by chromatin The Epc1 precipitates were subjected to immunoprecipitation with and it was that both Epc1 and SRF can with the SRE as a mechanism by which Epc1 mediates SRF we postulated that Epc1 may enhance the interaction of SRF to the chromatin immunoprecipitation, we the binding of SRF to the SRE in Epc1 knockdown H9c2 cells with that in cells. in Epc1 and protein were However, the of SRF were by Epc1 knockdown the of Epc1 expression caused a decrease in the binding of Epc1 to the SRE when the Epc1 was with antibody and Epc1 knockdown resulted in a decrease in SRF binding to the SRE and These results that Epc1 is required for the binding of SRF to the Epc1 to enhance the role of the polycomb group genes N. S. J. S. J. Dev. PubMed Scopus Google Scholar) by recruiting histone acetyltransferase in Drosophila Y. S. J. Cell. Biol. PubMed Scopus Google Scholar). The which Epc1, is known to and the acetylation is mediated by protein a family histone acetyltransferase Y. S. J. Cell. Biol. PubMed Scopus Google Scholar). These reports the that Epc1 may induce the acetylation of histone to although is known Epc1-mediated histone in mammalian cells or skeletal we the histone H3 and H4 acetylation of the SRE of the skeletal α-actin promoter by chromatin in the of both histones H3 and H4 associated with the SRE were However, the acetylation was in H9c2 cells, which suggests that Epc1 is for the histone acetylation of the We performed a histone acetyltransferase assay by using the protein of Epc1 in the but we Thus, we used Epc1 for the histone acetyltransferase assay and the acetylation of histone The of to that histone acetylation was mediated by other histone acetyltransferase proteins. immunoprecipitation assays were to the interaction of Epc1 and other histone acetyltransferase proteins. we Epc1 with by pCMV-myc-Epc1 or interacted with Epc1 However, a report that is in the skeletal muscle X. Lough J. PubMed Scopus Google Scholar) the of the interaction and Epc1 in skeletal muscle cells. we were to in H9c2 or C2C12 cells or in mouse muscle Thus, we postulated that a histone acetyltransferase other than may in the Epc1-mediated histone We immunoprecipitated Epc1 and histone acetyltransferase such as protein factor and p300 were p300, which is required for skeletal muscle gene transcription J. Y. L. Cell. Biol. PubMed Scopus Google Scholar), was of Epc1 in H9c2 cells resulted in a in the interaction with The Epc1 with p300 were also confirmed in C2C12 cells and in H9c2 cells The of p300 in the acetylation of the complex was confirmed by histone acetyltransferase after or knockdown of pCMX-p300 was histone acetylation was in the complex precipitates in a to Transfection of si-p300 the protein of p300 with si-p300 the histone acetyltransferase in Epc1 the biological role of Epc1, we generated Epc1 mice with cells The mice in However, Epc1 heterozygous mice for more than 6 phenotypes Epc1 expression was in the skeletal muscles of the heterozygous mice The expression of was also in the mice and In the Epc1 heterozygous the expression of skeletal α-actin was the we that skeletal α-actin was well with in the In the was in heterozygous group muscle differentiation in Epc1+/− muscle-specific gene expression in muscles from and Epc1+/− The expression of such as myogenin and MyoD, as well as of skeletal muscle-specific genes such as skeletal α-actin and was in heterozygous of skeletal α-actin, MyoD, and myogenin from mice and with gene expression in myoblasts obtained from and Epc1+/− The isolated myoblasts serum to induce differentiation for Skeletal muscle to be by serum in Epc1+/− serum of myoblasts obtained from and Epc1+/− The myoblasts were of serum and maintained for cells were were and the were performed in from with The levels and protein of muscle-specific genes or transcription factors in skeletal muscles were also than in We the muscle differentiation of the myoblasts was Although differentiation of isolated myoblasts by serum the expression of differentiation in the gene expression was as in myoblasts from heterozygous mice The in expression of the muscle-specific transcription factors resulted in a delay in the differentiation of the as by the multinucleated cells after serum In we that Epc1 is in skeletal muscle differentiation, which the that Epc1 may with other muscle-specific transcription factors to differentiation. We have that Epc1 with SRF, a of diverse muscle differentiation and cell survival (1Li S. Czubryt M.P. McAnally J. Bassel-Duby R. Richardson J.A. Wiebel F.F. Nordheim A. Olson E.N. Proc. Natl. Acad. Sci. U. S. A. 2005; 102: 1082-1087Crossref PubMed Scopus (230) Google M. Curr. Opin. Genet. Dev. 2001; 11: PubMed Scopus Google Scholar). We have that Epc1 to SRF and genes by recruiting p300, which induces skeletal muscle differentiation Epc1 is required for the activation of muscle-specific that muscle differentiation, such as and L. Richardson J.A. E. Olson E.N. Cell. 2001; Full Text Full Text PDF PubMed Scopus Google M. M.P. J. 2007; PubMed Scopus Google Scholar), are by which the of SRF in the of proteins. SRF, a MADS box transcription factor to is required for the differentiation of and muscle cells (1Li S. Czubryt M.P. McAnally J. Bassel-Duby R. Richardson J.A. Wiebel F.F. Nordheim A. Olson E.N. Proc. Natl. Acad. Sci. U. S. A. 2005; 102: 1082-1087Crossref PubMed Scopus (230) Google C. M. R. R. Cell. Full Text PDF PubMed Scopus Google J. Cell. Full Text Full Text PDF PubMed Scopus Google Zhang M. M. Nordheim A. Schwartz R.J. J. Biol. Chem. 2005; 280: Full Text Full Text PDF PubMed Scopus Google Scholar). SRF-dependent genes have sequences in promoter CArG and the binding of SRF to the promoter genes L. Richardson J.A. E. Olson E.N. Cell. 2001; Full Text Full Text PDF PubMed Scopus Google M. M.P. J. 2007; PubMed Scopus Google Scholar). Likewise, SRF-dependent muscle-specific genes have or more CArG MyoD is an of a transcription factor in the SRF-dependent of skeletal muscle SRF the transcription of MyoD by its binding to the CArG element in the regulatory in the promoter A. M. P. G. A. Biol. Cell. 14: PubMed Scopus Google Scholar). Likewise, skeletal α-actin an SRE in the promoter J.A. Booth F.W. J. Muscle Res. Cell 1998; 19: PubMed Scopus Google Scholar). we postulated that the of by Epc1 is mediated by the CArG box and that the promoter of skeletal α-actin containing the SRE was required for Epc1-mediated In this study, we that Epc1 to SRF to enhance the muscle differentiation in the myoblast cell skeletal α-actin CArG and both of which can to SRF L. McAnally J. Olson E.N. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). the CArG box sequences with site-directed we showed that the mouse box was responsible for Epc1-mediated was by the results of the chromatin immunoprecipitation assay using antibody in H9c2 cells. The SRE in the skeletal α-actin promoter was amplified from the with which suggests that the complex to the when we used the in Epc1 expression in the Epc1 knockdown cells resulted in a decrease in the binding of SRF to the These results suggest that the complex the SRE and that Epc1 is required for the activation of SRF-dependent transcriptional histone acetyltransferase activity, which is mediated by histone acetyltransferase such as p300, a of protein and (3McKinsey T.A. Zhang C.L. Olson E.N. Curr. Opin. Genet. Dev. 2001; 11: 497-504Crossref PubMed Scopus (352) Google La J. Cell Sci. 2001; PubMed Google J. Biochem. Cell Biol. 2006; PubMed Scopus Google M. R. J. M. R. J. Y. Cell. 2000; 102: Full Text Full Text PDF PubMed Scopus Google Scholar). the histone induce of genes by in the of the promoter G. EMBO PubMed Scopus Google Scholar). In a of as a of the this complex histone acetyltransferase that is mediated by N. S. J. S. J. Dev. PubMed Scopus Google Scholar). In is known to with SRF and to development Dev. PubMed Scopus Google Scholar) by factor X. C. Lough J. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). However, in this study, although to Epc1, it was in skeletal an histone p300, which is in skeletal was recruited by is that histone acetyltransferase mediated by p300 is for by a complex to the gene family R. E. Dev. 1996; PubMed Scopus Google Scholar) or by association with SRF to induce CArG genes A. M. P. G. A. Biol. Cell. 14: PubMed Scopus Google Y. R.J. J. Biol. Chem. 2005; 280: Full Text Full Text PDF PubMed Scopus Google Scholar). In histone acetyltransferase is required for myogenesis from cells N. C. S. J. H. M. R. EMBO J. PubMed Scopus Google Scholar), p300 as a of the Thus, we have that p300 is a of the complex that skeletal muscle-specific in the of the phenotypes in Epc1 heterozygous mice the of Epc1 in skeletal muscle Although Epc1 heterozygous mice can in the expression levels of the muscle-specific transcription factors were and the were the differentiation of isolated by serum was which suggests a for Epc1 in the is that skeletal α-actin was also in mice that SRF also an important role in the of as well as in the expression of X. K. J. Cell 2007; PubMed Scopus Google Scholar), Epc1 also to be required for the of although this will it is Epc1 a role in transcriptional and its or its of transcriptional activity. Epc1 be a that as a of the However, in Epc1 in muscle differentiation as a modulator of SRF. We are to Jeong Kim of for in the with