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Dynamic Interactions of Chromatin-Related Mesenchymal Modulator, a Chromodomain [复制链接]

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发表于 2009-3-5 00:06 |只看该作者 |倒序浏览 |打印
作者:Irena Shur, Ronit Solomon, Dafna Benayahu作者单位:Department of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel 6 u; }* }; C8 ]0 s0 z
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! Y* m" i- _4 L7 d0 ]) L          【摘要】& V4 t6 n8 s- @% Y
      The newly identified protein chromatin-related mesenchymal modulator (CReMM) is expressed by marrow stromal progenitors in vivo and ex vivo. CReMM belongs to a recently identified subgroup of chromodomain helicase-DNA-binding proteins composed of multiple domains including chromodomains, SNF2/ATPase, helicase-C domain, SANT, and A/T-hook-DNA binding domain. Chromatin immunoprecipitation assay was applied to follow the dynamics of CReMM binding to A/T-rich regions on promoters of genes that play a role in osteoblast maturation. CReMM interaction with BMP4 and biglycan promoters in the marrow stromal cells was challenged with transforming growth factor-ß. Treatment with 17ß-estradiol enhanced the binding to estrogen receptor and abolished binding to the prolactin receptor promoters; CReMM interaction with osteocalcin promoter was identified constantly. CReMM binding to the analyzed endogenous promoters suggests its direct role in the transcriptional program activated during osteogenic cell differentiation, which may be a useful tool for following the molecular mechanism of the "stemness" of mesenchymal cells.
6 s' N" \  {. I. r$ M. ?, T          【关键词】 Differentiation CHD Promoters Progenitors- i& m. A& {# f* `
                  INTRODUCTION8 s. @5 }- N% ]5 K. L' R# a) V

7 v% C. Y  z  C9 W' W4 K/ ~1 ?, PThe fate of mesenchymal stem cells during differentiation is determined by a cascade of events that depends on the timed and coordinated readout of the compacted DNA in the nucleus. Nucleosomes restrict the accession of transcription machinery to specific regulatory regions of the DNA. Therefore, only a relatively small number of genes are read and used, with the rest remaining repressed. Various regulatory elements act as binding sites for distinct factors to bind to the promoters, resulting in gene-specific transcription in cells and tissues. The transcription regulation of differentiating skeletal cells from mesenchymal precursors is a complex process, involving multiple factors. The challenge is to understand how regulatory signals affect gene expression in a promoter-dependent manner through the cooperation of multiprotein complexes that regulate chromatin remodeling. Other levels affecting the cellular and molecular regulation of stem cells include cell-cell and extracellular matrix interactions that switch on the regulatory mechanisms integrated at different hierarchical levels. Regulation of transcript turnover and translational control are an integral part of cell- and tissue-specific gene expression. Variety of post-translational modification processes are known to affect the stability and three-dimensional structure of proteins and consequently their functions.
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- W# R. p0 s. z8 o$ CSystemic hormones and growth factors regulate the skeleton physiology .4 u0 U* Y8 l8 t/ L7 N- G

$ u2 U& J/ E1 m4 i4 BChromatin-related mesenchymal modulator (CReMM) protein is a chromodomain helicase-DNA-binding (CHD) family member that is expressed by osteoprogenitors both in vivo and in vitro was described by us recently . The protein discloses multiple domains that relate its activity to the control of transcription regulation. In this study, we followed the dynamic changes in the occupancy of specific endogenous promoters in primary bone marrow stromal cells that posses an osteogenic potential. Specific interaction between partial CReMM peptide with DNA elements on the amplified promoters was demonstrated by electrophoresis mobility shift assay (EMSA). CReMM interaction with A/T-rich regions on promoters appeared to be sensitive to treatment with transforming growth factor-ß (TGFß) and 17ß-estradiol, factors known to affect early stages of osteoblastic differentiation. These results suggest that CReMM has a potential role in the transcription regulation of osteogenic cells.
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3 {) E% P. t: o5 y( QMATERIALS AND METHODS
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In Vitro Culture; @2 H& k5 O  P( R: }
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Human bone marrow stromal cell (MSC) culture was previously described in detail . Cells were cultured in Dulbecco¡¯s modified Eagle¡¯s medium (Gibco, Grand Island, NY, http://www.invitrogen.com) with the addition of 10% heat-inactivated fetal calf serum (Gibco). When indicated, MSCs were treated with 10¨C8 M 17ß-estradiol (17ß-E2; Sigma-Aldrich, St. Louis, http://www.sigmaaldrich.com) or with 5 ng/ml TGFß (Collaborative Research, Bedford, MA) for 24 hours in culture prior to analysis.
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Antibodies
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" ]$ u" S* i3 N. {$ CAnti-CReMM , anti-estrogen receptor (anti-ER) (Upstate Biotechnology, http://www.upstatebiotech.com) and anti-pc-Jun (sc-822, Santa Cruz Biotechnology Inc., Santa Cruz, CA, http://www.scbt.com) were applied for the chromatin immunoprecipitation (ChIP) analysis.# t. I. K) \- {! w3 L  _6 O% b
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Chromatin Immunoprecipitation5 H: A4 j3 O+ _
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The ChIP technique is based on formaldehyde fixation of DNA-protein complexes (http://www.upstatebiotech.com). After fixation, the chromatin fraction from MSCs was sheared, and CReMM-specific fragments were precipitated with anti-CReMM antibody. In some experiments, ChIP was performed with anti-ER and anti-pc-Jun. The ChIP was performed using CReMM-specific antibody to analyze 1) the precipitated protein from the DNA-protein complex, which was separated on SDS-polyacrylamide gel electrophoresis (PAGE) gel and verified by Western blot for CReMM; and 2) DNA purified from the isolated protein-DNA immunocomplex, which was analyzed for CReMM interactions with individual promoters. DNA was isolated upon reversal of the formaldehyde cross-linking and was used as a template for polymerase chain reaction (PCR) amplification with primers specific to the selected promoters. Promoters were chosen based on data available from the gene bank and analyzed using bioinformatics tools, including analysis for A/T-rich stretches as described previously (http://www.opd.tau.ac.il) . We focused on promoters for BMP4, prolactin receptor (PRLR), ER, osteocalcin (OC) and biglycan. ChIP analysis was performed with cells obtained from several donors (n = 5¨C9).
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Immunoprecipitation, SDS-PAGE Gels, and Western Blot Analysis7 w' G. \9 t$ {; P
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These assays were performed according to the standard protocols (http://www.protocol-online.net). Briefly, immunoprecipitation was performed with CReMM antibody incubated overnight with protein A immobilized on Sepharose CL-4B (Pfizer Global R&D, Cambridge, MA, http://www.pfizerrtc.com). The immunocomplexes were separated on 6.5% SDS-PAGE gel for 2 hours and then transferred to the nitrocellulose blots and probed with primary antibody to CReMM. Incubation with the primary antibody for 1 hour was followed by incubation with secondary antibody goat anti-rabbit biotin IgG (DAKO, Glostrup, Denmark, http://www.dako.com) and extravidin-peroxidase (Sigma-Aldrich) for detection with chemiluminescent substrate (Pierce, Rockford, IL, http://www.piercenet.com).
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8 R2 m- f! C+ l+ ePCR Amplification8 e* n$ g1 H; F- U& d

$ y( n4 i3 ^. t2 LThe isolated DNA from ChIP protein-DNA complex was used as template for PCR amplification of selected promoter regions with Taq polymerase (Takara, Otsu, Japan, http://www.takara.co.jp) and specific primers (Table 1). The amplified immunoprecipitated DNA was compared with DNA from corresponding input chromatin fraction, and each PCR was performed at least twice. The reaction products were separated by electrophoresis in 1% agarose gels (SeaKem GTG FMC; Cambrex BioScience Rockland, Inc., Rockland, ME, http://www.cambrex.com) in Tris Borate EDTA (TBE) buffer. The amplified DNA fragments were stained by ethidium bromide, and their optical density was measured using Bio Imaging System (BIS 202D).
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Table 1. Primers for chromatin immunoprecipitation analysis3 J% N" Q" P6 @2 s: K* I. H' c
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Electrophoresis Mobility Shift Assay
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EMSA was performed with recombinant protein (rP) (2332¨C2481 amino acids) and 32P-labeled PCR product of specific promoter region. Binding reaction with 1 µg of rP and 100,000 cpm of 32P-labeled probe was carried in 20 µl of binding buffer (26 mM Hepes , which competed with the binding between A/T-rich probes and the rP. The samples were incubated for 15 minutes at room temperature prior to loading in 5% native polyacrylamide gel in 0.25 M TBE. The gels were run for 40 minutes at room temperature in TBE buffer and then were dried and autoradiographed using X-OMAT AR (Kodak).
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' j/ d* `' [% i1 `RESULTS
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+ T/ W: i- f4 ^CReMM is a chromatin remodeling protein, related to the CHD family, expressed by osteoprogenitors in bone section in vivo and by cultured stromal cells derived from the bone marrow. We have shown that CReMM disclosed both A/T-hook-like DNA binding and ATPase activity . The A/T-rich elements are embedded in promoters and play a role in the regulation of gene transcription by binding A-T-hook proteins. We identified A/T-rich regions for promoters of PRLR, ER, BMP4, biglycan, and OC genes (Figs. 1, 2; Table 1). We employed ChIP to investigate the association of CReMM with these promoters in ex vivo MSC cultures. The specificity of immunoprecipitated chromatin fraction was verified by SDS-PAGE and Western blot with anti-CReMM antibody (Fig. 1E). PCR analysis of the purified DNA from the immunoprecipitated chromatin fraction revealed that CReMM was associated with OC promoter (Fig. 1F) and PRLR (Fig. 2B) but was not present on the BMP4, biglycan, or ER promoters (Fig. 1F). Treatment of MSCs with 17ß-E2 led to de novo interaction of CReMM with the ER promoter (Fig. 2F) and disappearance from the promoter of PRLR (Fig. 2B, lane 3). In contrast, stimulation of cells with TGFß enabled CReMM binding to the BMP4 and biglycan promoters (Fig. 1F). The OC promoter was occupied constitutively by the protein, and this interaction was not affected upon challenging of MSCs with either 17ß-E2 or TGFß. Amplified promoter regions from BMP4 and ER genes were used as probes for EMSA analysis with partial CReMM recombinant protein fragment containing the DNA binding domain (rP, residues 2332¨C2481 amino acids). The formation of the specific CReMM-DNA complex indicates the capability of binding to the A/T-rich region in analyzed promoters (Fig. 1G, lanes 2, 5), which was abolished in the presence of distamycin A (Fig. 1G, lanes 3, 6).5 i( ]# n9 A- O# l: p( |
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Figure 1. A/T-rich analysis of promoter regions of ER (A), BMP4 (B), biglycan (C), and OC (D) genes. Graphs present the relative position (in base pairs) of the matrix association potential region upstream to the transcription start site. (E): Western blot analysis of chromatin-related mesenchymal modulator (CreMM) protein immunoprecipitated from chromatin fraction with anti-CReMM antibody. (F): ChIP assay of CReMM binding to different promoters of ER, BMP4, byglican, and OC genes amplified by polymerase chain reaction (PCR) from C, E2, or TGF. DNA quality was analyzed in corresponding input chromatin fraction. (G): PCR products amplified from ChIP samples were used as probes for electrophoresis mobility shift assay analysis to BMP4 (lanes 1¨C3) and ER (lanes 4¨C6) promoter probes. Lanes 1 and 4 correspond to radiolabeled probes; lanes 2 and 5 correspond to hybrid of probe with recombinant protein (rp) CReMM; and lanes 3 and 6 demonstrate abolishment of hybridization with rpCReMM in the presence of distamycin A. Abbreviations: C, untreated cells; ChIP, chromatin immunoprecipitation; E2, 17ß-E2; ER, estrogen receptor; OC, osteocalcin; TGF, transforming growth factor ß-treated.
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Figure 2. ChIP assay of CReMM binding to prolactin receptor promoter. (A): Bioinformatic analysis of A/T-rich regions, AP-1 (square), and ER-response elements (circle). Graph presents the relative position (in the base pairs) of the matrix association potential region upstream to the transcription start site. (B): DNA obtained from ChIP with anti-CReMM, anti-ER, and anti-p-cJUN from C and E2 cells. The DNA quality was analyzed in the corresponding input chromatin fraction. Abbreviations: C, untreated cells; ChIP, chromatin immunoprecipitation; CReMM, chromatin-related mesenchymal modulator; E2, 17ß-E2 treated; ER, estrogen receptor.: e5 a0 B+ K" K/ A/ `7 X
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We analyzed the interactions of CReMM with a promoter of PRLR that is regulated by 17ß-E2 (Fig. 2). 17ß-E2 binds to its receptors and transduces the signals through binding either to the promoters directly or in cooperation with the AP-1 transcription factor complex. In addition to the A/T rich region, the PRLR promoter contains ER-response elements and AP-1 binding sites. We applied ChIP with antibodies for CReMM, ER, and p-cJun to analyze the interactions of these regulatory factors with the PRLR promoter in the presence or absence of 17ß-E2. The ChIP analysis showed occupancy of the PRLR promoter by all three proteins in untreated cultures (Fig. 2B). In contrast, the binding of CReMM, ER, and p-cJun to the PRLR promoter was abolished in cells treated with 17ß-E2 (Fig. 2B).
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/ K: I! g% F7 K. s# ^6 qIn summary, the interactions of CReMM with various promoters of bone-related genes were studied in MSCs. According to our results, CReMM does not bind to the promoters of ER, BMP4, and biglycan genes in control MSCs. However, de novo binding to the ER promoter was achieved following 17ß-E2 treatment of cells, and binding to the BMP4 and biglycan promoters was stimulated by TGFß. The promoter of OC, a bone-matrix protein expressed in mature cells, was occupied by CReMM in all culture conditions. In untreated MSCs, we identified binding of ER, CReMM, and p-cJun to the PRLR promoter, which was negatively regulated by 17ß-E2.
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DISCUSSION3 d" C8 P! u2 ]8 m
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CReMM is a new CHD-related protein that presumably functions as a chromatin modifying factor expressed by osteoprogenitors in vivo and by MSCs in vitro . The multiple differentiation potential of MSCs makes them a powerful tool for future cell-therapy modalities. Accomplishment of such a task requires better characterization of molecular mechanisms that trigger the stemness potential of MSCs.
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0 f; D1 g5 I; l, O5 LThe remodeling of chromatin structure facilitates the access of transcription factors to DNA by repositioning nucleosomes at the promoter region .: V) H1 L( o" k+ ?% i3 ~
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Given that CReMM is expressed by osteoprogenitors, we suggest its role in transcriptional response to systemic hormones and growth factors. We treated cells with TGFß or 17ß-E2, which affect the cells at the proliferative stages. TGFß induces cells at early stages of chondroblastic and osteoblastic differentiation but inhibits myogenesis, adipogenesis, and late-stage osteoblast differentiation . Our findings show that occupation of the PRLR promoter by CReMM, ER, and p-cJUN is modulated by 17ß-E2 in a similar way. The results suggest that CReMM, a chromatin remodeler, directly reorganizes chromatin that affects the binding of transcription factors.
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In summary, CReMM is a new member of the CHD family that possesses a DNA-dependent ATPase activity and binds to A/T-rich regulatory regions of various promoters. It binds to promoters in a differential pattern modulated by TGFß and 17ß-E2. Demonstrated dynamic interactions of endogenous CReMM with the regulatory regions of promoters that are critical to osteoblastogenesis suggest a possible role of CReMM in the transcriptional program in osteoprogenitors and its possible influence on the direction of mesenchymal stem cell maturation. CReMM is a chromatin-remodeling protein with a putative role in the epigenetic control of particular genes along the osteogenesis pathway; it may be helpful in the identification of the cascade of regulatory factors in the commitment and differentiation of mesenchymal cells.( _; v! [7 z, g) T+ u* H: ^
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ACKNOWLEDGMENTS5 m" T0 I2 G) K& T1 D+ G
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This study was supported by grants from the Greidinger Fund for Cancer Research and the Chief Scientist, Ministry of Health (to B.D.).
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The authors indicate no potential conflicts of interest.
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Clement-Lacroix P, Ormandy C, Lepescheux L et al. Osteoblasts are a new target for prolactin: Analysis of bone formation in prolactin receptor knockout mice. Endocrinology 1999;140:96¨C105., l( e+ O, J! ^( c

' Z1 g9 @. O5 q0 eNanbu-Wakao R, Fujitani Y, Masuho Y et al. Prolactin enhances CCAAT enhancer-binding protein-beta (C/EBP beta) and peroxisome proliferator-activated receptor gamma (PPAR gamma) messenger RNA expression and stimulates adipogenic conversion of NIH-3T3 cells. Mol Endocrinol 2000;14:307¨C316.; r* F& u3 E7 ?) Y" l; c

  @9 I3 q& u. C; `. T/ p9 \( h% {Zhou S, Turgeman G, Harris SE et al. Estrogens activate bone morphogenetic protein-2 gene transcription in mouse mesenchymal stem cells. Mol Endocrinol 2003;17:56¨C66.& ~7 T  r" E: l+ C
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Karsenty G. Minireview: Transcriptional control of osteoblast differentiation. Endocrinology 2001;142:2731¨C2733.
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Lian JB, Javed A, Zaidi SK et al. Regulatory controls for osteoblast growth and differentiation: Role of Runx/Cbfa/AML factors. Crit Rev Eukaryot Gene Expr 2004;14:1¨C41.
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! }2 z. ^& e! r" yOlsen BR, Reginato AM, Wang W. Bone development. Annu Rev Cell Dev Biol 2000;16:191¨C220.% `$ _6 l7 F0 g& t
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Janssens K, Ten Dijke P, Janssens S et al. Transforming growth factor-µ1 to the Bone. Endocr Rev 2005;26:743¨C774.
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Barkhem T, Nilsson S, Gustafsson JA. Molecular mechanisms, physiological consequences and pharmacological implications of estrogen receptor action. Am J Pharmacogenomics 2004;4:19¨C28., [7 ~4 |) L2 L
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沙发
发表于 2015-7-3 10:38 |只看该作者
对不起,我走错地方了,呵呵  

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藤椅
发表于 2015-7-13 17:10 |只看该作者
声明一下:本人看贴和回贴的规则,好贴必看,精华贴必回。  

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板凳
发表于 2015-7-30 12:27 |只看该作者
干细胞之家微信公众号
我该不会是最后一个顶的吧  

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报纸
发表于 2015-8-2 19:02 |只看该作者
真是有你的!  

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地板
发表于 2015-8-7 12:43 |只看该作者
心脏干细胞

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发表于 2015-8-7 20:06 |只看该作者
我想要`~  

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发表于 2015-8-30 15:16 |只看该作者
哈哈,有意思~顶顶 ,继续顶顶。继续顶哦  

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发表于 2015-9-13 16:04 |只看该作者
干细胞治疗  

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发表于 2015-9-24 17:01 |只看该作者
顶也~  
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