mAM Facilitates Conversion by ESET of Dimethyl to Trimethyl Lysine 9 of Histone H3 to Cause Transcriptional Repression

Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Molecular Cell (Impact Factor: 14.02). 09/2003; 12(2):475-87. DOI: 10.1016/j.molcel.2003.08.007
Source: PubMed


Methylation of histone tails plays an important role in chromatin structure and function. Previously, we reported that ESET/SETDB1 is a histone methyltransferase (HMTase). Here, we show that SETDB1 tightly associates with the human homolog of mAM, a murine ATFa-associated factor. Although recombinant ESET can methylate lysine 9 of histone H3 (H3-K9), its activity is severely compromised when compared to that of the ESET/mAM complex. mAM stimulates ESET enzymatic activity by increasing the Vmax and decreasing the Km. Importantly, mAM facilitates the ESET-dependent conversion of dimethyl H3-K9 to the trimethyl state both in vitro and in vivo. Chromatin-based transcription and ChIP analyses demonstrate that mAM enhances ESET-mediated transcriptional repression in a SAM-dependent manner, and this repression correlates with H3-K9 trimethylation at the promoter. Thus, our studies establish that promoter H3-K9 trimethylation is the cause of transcriptional repression and that mAM/hAM facilitates conversion of H3-K9 dimethyl to trimethyl by ESET/SETDB1.

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Available from: Hediye Erdjument-Bromage, May 05, 2015
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    • "SET domain, bifurcated 1 (SETDB1) is a histone methyltransferase (HMT) that methylates lysine 9 on histone H3 (H3K9) [12]. The enzymatic activity of SETDB1, in association with MBD1- containing chromatin-associated factor 1 (MCAF1), converts H3K9me2 to H3K9me3 and represses subsequent transcription [8] [13]. SETDB1 is amplified in cancers such as melanoma and lung cancer, and increased expression of SETDB1 promotes tumorigenesis in a zebrafish melanoma model [14] [15]. "
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    ABSTRACT: SET domain, bifurcated 1 (SETDB1) is a histone methyltransferase that methylates lysine 9 on histone H3. Although it is important to know the localization of proteins to elucidate their physiological function, little is known of the subcellular localization of human SETDB1. In the present study, to investigate the subcellular localization of hSETDB1, we established a human cell line constitutively expressing enhanced green fluorescent protein fused to hSETDB1. We then generated a monoclonal antibody against the hSETDB1 protein. Expression of both exogenous and endogenous hSETDB1 was observed mainly in the cytoplasm of various human cell lines. Combined treatment with the nuclear export inhibitor leptomycin B and the proteasome inhibitor MG132 led to the accumulation of hSETDB1 in the nucleus. These findings suggest that hSETDB1, localized in the nucleus, might undergo degradation by the proteasome and be exported to the cytosol, resulting in its detection mainly in the cytosol. Copyright © 2015. Published by Elsevier Inc.
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    • "Methylation of H3 on lysine 9 (H3K9me) is associated with gene silencing and mediated by histone lysine methyltransferases (HKMT) including SETDB1 [14] [15] [16] [17]. "
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    ABSTRACT: Maintenance of the covalently closed circular HBV DNA (cccDNA) that serves as a template for HBV transcription is responsible for the failure of antiviral therapies. While studies in chronic hepatitis patients have shown that high viremia correlates with hyperacetylation of cccDNA-associated histones, the molecular mechanisms controlling cccDNA stability and transcriptional regulation are still poorly understood. This study aimed to decipher the role of chromatin and chromatin modifier proteins on HBV transcription. We analyzed the chromatin structure of actively transcribed or silenced cccDNA by infecting primary human hepatocytes and differenciated hepaRG cells with wild type virus or virus deficient (HBV X-) for the expression of Hepatitis B Virus X protein (HBx), that is required for HBV expression. In the absence of HBx, HBV cccDNA was transcriptionally silenced with the concomitant decrease of histone 3 (H3) acetylation and H3K4me3, increase of H3 di- and tri-methylation (H3K9me) and the recruitment of heterochromatin protein 1 factors (HP1) that correlate with condensed chromatin. SETDB1 was found to be the main histone methyltransferase responsible for the deposition of H3K9me3 and HBV repression. Finally, full transcriptional reactivation of HBVX- upon HBx re-expression correlated with an increase of histone acetylation and H3K4me3, and a concomitant decrease of HP1 binding and of H3K9me3 on the cccDNA. Upon HBV infection, cellular mechanisms involving SETDB1-mediated H3K9me3 and HP1 induce silencing of HBV cccDNA transcription through modulation of chromatin structure. HBx is able to relieve this repression and allow the establishment of active chromatin. Copyright © 2015. Published by Elsevier B.V.
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    • "Methylation at these sites leads to gene silencing through the binding of histone methyl domain binding proteins (Adams-Cioaba & Min, 2009). G9a and GLP are the main enzymes responsible for catalyzing H3K9me2 modifications (Shinkai & Tachibana, 2011; Tachibana et al., 2005), and SETDB1 can catalyze the formation of both H3K9me2 and H3K9me3 (Wang et al., 2003; Zee et al., 2010). "
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