The specific post-translational modifications to histones influence many nuclear processes including gene regulation, DNA repair and replication. Recent studies have identified effector proteins that recognize patterns of histone modification and transduce their function in downstream processes. For example, histone acetyltransferases (HATs) have been shown to participate in many essential cellular processes, particularly those associated with activation of transcription. Yeast SAGA (Spt-Ada-Gcn5 acetyltransferase) and SLIK (SAGA-like) are two highly homologous and conserved multi-subunit HAT complexes, which preferentially acetylate histones H3 and H2B and deubiquitinate histone H2B. Here we identify the chromatin remodelling protein Chd1 (chromo-ATPase/helicase-DNA binding domain 1) as a component of SAGA and SLIK. Our findings indicate that one of the two chromodomains of Chd1 specifically interacts with the methylated lysine 4 mark on histone H3 that is associated with transcriptional activity. Furthermore, the SLIK complex shows enhanced acetylation of a methylated substrate and this activity is dependent upon a functional methyl-binding chromodomain, both in vitro and in vivo. Our study identifies the first chromodomain that recognizes methylated histone H3 (Lys 4) and possibly identifies a larger subfamily of chromodomain proteins with similar recognition properties.
"Double chromodomains of human CHD1 are associated with methylated histone H3 lysine 4 (H3K4me) which is a hallmark of active chromatin (Flanagan et al., 2005). Yeast Chd1 regulates transcription by interacting with SAGA complex which contains histone acetyltransferase and Drosophila CHD1 is required for histone H3.3 deposition demonstrating that the proteins in Chd1 subfamily are positively involved in transcription regulation (Pray-Grant et al., 2005; Konev et al., 2007). In Mi-2 subfamily, two PHD finger domains at N-terminal of human CHD4 bind to histone tails, while the double chromodomains of dMi-2 display DNA binding activity (Bouazoune et al., 2002; Mansfield et al., 2011). "
[Show abstract][Hide abstract] ABSTRACT: Chromodomain-Helicase-DNA (CHD)-binding proteins have been characterized in various species as important transcription regulators by their chromatin remodeling activity. However, in plant the function of these proteins has hardly been analyzed before except that Arabidopsis PIKLE and rice CHR729 are identified to play critical roles in the regulation of series of genes involved in developmental or stress responding process. In this review we focus on how plant CHD proteins regulate gene expression and the role of these proteins in controlling plant development and stress response.
"Histone methylation can contribute to transcriptional regulation by recruiting transcription complexes which contain HAT activity. For example, the chromodomain of the chromatin remodelling protein Chd1 binds to methylated H3-K4, recruiting the yeast SAGA (Spt-Ada-Gcn5 HAT) complex which contains the H3 HAT GCN5 . In the context of the present study, by governing histone acetylation status and the accessibility of STAT6 to the 15-LOX-1 promoter, SMYD3-mediated H3-K4 methylation may function as a critical element licensing 15-LOX-1 gene expression. "
[Show abstract][Hide abstract] ABSTRACT: 15-Lipoxygenase-1 (15-LOX-1) oxidizes polyunsaturated fatty acids to a rich spectrum of biologically active metabolites and is implicated in physiological membrane remodelling, inflammation and apoptosis. Its deregulation is involved in the pathogenesis of diverse cancer and immune diseases. Recent experimental evidence reveals that dynamic histone methylation/demethylation mediated by histone methyltransferases and demethylases plays a critical role in regulation of chromatin remodelling and gene expression. In the present study, we compared the histone 3 lysine 4 (H3-K4) methylation status of the 15-LOX-1 promoter region of the two Hodgkin lymphoma (HL) cell lines L1236 and L428 with abundant and undetectable 15-LOX-1 expression, respectively. We identified a potential role of H3-K4 methylation in positive regulation of 15-LOX-1 transcription. Furthermore, we found that histone methyltransferase SMYD3 inhibition reduced 15-LOX-1 expression by decreasing promoter activity in L1236 cells. SMYD3 knock down in these cells abolished di-/trimethylation of H3-K4, attenuated the occupancy by the transactivator STAT6, and led to diminished histone H3 acetylation at the 15-LOX-1 promoter. In contrast, inhibition of SMCX, a JmjC-domain-containing H3-K4 tri-demethylase, upregulated 15-LOX-1 expression through induction of H3-K4 trimethylation, histone acetylation and STAT6 recruitment at the 15-LOX-1 promoter in L428 cells. In addition, we observed strong SMYD3 expression in the prostate cancer cell line LNCaP and its inhibition led to decreased 15-LOX-1 expression. Taken together, our data suggest that regulation of histone methylation/demethylation at the 15-LOX-1 promoter is important in 15-LOX-1 expression.
PLoS ONE 12/2012; 7(12):e52703. DOI:10.1371/journal.pone.0052703 · 3.23 Impact Factor
"Furthermore, Ubp8, Sus1, Sgf11 and Sgf73 have been shown to be components of the DUB module , , . The Chd1 protein has also been found to be associated with the SAGA complex , but this result was not confirmed by another study . "
[Show abstract][Hide abstract] ABSTRACT: Interleukin-1α (IL-1α) is a proinflammatory cytokine and a key player in host immune responses in higher eukaryotes. IL-1α has pleiotropic effects on a wide range of cell types, and it has been extensively studied for its ability to contribute to various autoimmune and inflammation-linked disorders, including rheumatoid arthritis, Alzheimer's disease, systemic sclerosis and cardiovascular disorders. Interestingly, a significant proportion of IL-1α is translocated to the cell nucleus, in which it interacts with histone acetyltransferase complexes. Despite the importance of IL-1α, little is known regarding its binding targets and functions in the nucleus. We took advantage of the histone acetyltransferase (HAT) complexes being evolutionarily conserved from yeast to humans and the yeast SAGA complex serving as an epitome of the eukaryotic HAT complexes. Using gene knock-out technique and co-immunoprecipitation of the IL-1α precursor with TAP-tagged subunits of the yeast HAT complexes, we mapped the IL-1α-binding site to the HAT/Core module of the SAGA complex. We also predicted the 3-D structure of the IL-1α N-terminal domain, and by employing structure similarity searches, we found a similar structure in the C-terminal regulatory region of the catalytic subunit of the AMP-activated/Snf1 protein kinases, which interact with HAT complexes both in mammals and yeast, respectively. This finding is further supported with the ability of the IL-1α precursor to partially rescue growth defects of snf1Δ yeast strains on media containing 3-Amino-1,2,4-triazole (3-AT), a competitive inhibitor of His3. Finally, the careful evaluation of our data together with other published data in the field allows us to hypothesize a new function for the ADA complex in SAGA complex assembly.
PLoS ONE 08/2012; 7(8):e41801. DOI:10.1371/journal.pone.0041801 · 3.23 Impact Factor
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