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C Bean, N K Verma, D L Yamamoto, F Chemello, V Cenni, M C Filomena, J Chen, M L Bang, G Lanfranchi
Adaptive responses of skeletal muscle regulate the nuclear shuttling of the sarcomeric protein Ankrd2 that can transduce different stimuli into specific adaptations by interacting with both structural and regulatory proteins. In a genome-wide expression study on Ankrd2-knockout or -overexpressing primary proliferating or differentiating myoblasts, we found an inverse correlation between Ankrd2 levels and the expression of proinflammatory genes and identified Ankrd2 as a potent repressor of inflammatory responses through direct interaction with the NF-κB repressor subunit p50...
January 16, 2014: Cell Death & Disease
Smitha Pillai, Karoly Szekeres, Nicholas J Lawrence, Srikumar P Chellappan, George Blanck
The induction of the major histocompatibility (MHC), antigen-presenting class II molecules by interferon-gamma, in solid tumor cells, requires the retinoblastoma tumor suppressor protein (Rb). In the absence of Rb, a repressosome blocks the access of positive-acting, promoter binding proteins to the MHC class II promoter. However, a complete molecular linkage between Rb expression and the disassembly of the MHC class II repressosome has been lacking. By treating A549 lung carcinoma cells with a novel small molecule that prevents phosphorylation-mediated, Rb inactivation, we demonstrate that Rb represses the synthesis of an MHC class II repressosome component, YY1...
January 10, 2013: Gene
Qin Yan, Ruaidhri J Carmody, Zhonghua Qu, Qingguo Ruan, Jennifer Jager, Shannon E Mullican, Mitchell A Lazar, Youhai H Chen
Sustained Toll-like receptor (TLR) stimulation continuously activates antimicrobial genes but paradoxically represses inflammatory genes. This phenomenon, termed TLR tolerance, is essential for preventing fatal inflammatory conditions such as sepsis, but its underlying mechanisms are unclear. We report here that NF-κB binding nucleic acids of gene promoters are tolerogenic motifs, which selectively recruit an NcoR-Hdac3-deacetylated-p50 repressosome to inflammatory genes. Genome-wide analyses of TLR4-induced genes revealed that NF-κB motifs were the only regulatory elements significantly enriched in tolerizable genes...
August 28, 2012: Proceedings of the National Academy of Sciences of the United States of America
Rocío González-Lamothe, Patrick Boyle, Annie Dulude, Vicky Roy, Cyr Lezin-Doumbou, Gidda Satinder Kaur, Kamal Bouarab, Charles Després, Normand Brisson
Transcriptional reprogramming is critical for plant disease resistance responses. In potato (Solanum tuberosum), the marker gene PATHOGENESIS-RELATED-10a (PR-10a) is transcriptionally activated by pathogens, wounding, or elicitor treatment. Activation of PR-10a requires the recruitment of the activator Why1 to its promoter. In addition, PR-10a is negatively regulated by the repressor SEBF (for Silencer Element Binding Factor). Here, we show through a yeast two-hybrid screen that SEBF interacts with Pti4, which has been shown to be a transcriptional activator...
November 2008: Plant Cell
Lark Kyun Kim, Un Yung Choi, Hwan Sung Cho, Jung Seon Lee, Wook-bin Lee, Jihyun Kim, Kyoungsuk Jeong, Jaewon Shim, Jeongsil Kim-Ha, Young-Joon Kim
The activation of several transcription factors is required for the elimination of infectious pathogens via the innate immune response. The transcription factors NF-kappaB, AP-1, and STAT play major roles in the synthesis of immune effector molecules during innate immune responses. However, the fact that these immune responses can have cytotoxic effects requires their tight regulation to achieve restricted and transient activation, and mis-regulation of the damping process has pathological consequences. Here we show that AP-1 and STAT are themselves the major inhibitors responsible for damping NF-kappaB-mediated transcriptional activation during the innate immune response in Drosophila...
September 2007: PLoS Biology
Szabolcs Semsey, Konstantin Virnik, Sankar Adhya
The gal operon of Escherichia coli is negatively regulated by the Gal repressosome, a higher order nucleoprotein complex containing a DNA loop that encompasses two gal promoters. In the repressosome structure, Gal repressor (GalR) dimers are bound to the two operator sites, flanking the promoter region, thus generating a DNA loop. The DNA loop is stabilized by binding of the architectural HU protein to the apex of the loop, and negative supercoiling. The gal promoters are also regulated in opposite directions by GalR without DNA looping...
April 28, 2006: Journal of Molecular Biology
Siddhartha Roy, Emilios K Dimitriadis, Sudeshna Kar, Mark Geanacopoulos, Marc S Lewis, Sankar Adhya
DNA transaction reactions require formation of nucleoprotein complexes that involve multifaceted DNA-protein and protein-protein interactions. Genetic and biochemical studies suggested that the higher order Gal repressosome structure, which governs the transcription of two tandem galpromoters in Escherichia coli, involves sequence-specific binding of GalR repressor dimers to two operators, O(E) and O(I), located 113 bp apart, binding of GalR to the sequence-nonspecific DNA binding protein HU, interaction of HU with an architecturally critical DNA site between the two operators, and interaction between two DNA-bound GalR dimers generating a loop of the intervening DNA segment...
April 12, 2005: Biochemistry
Brian Lee, Constantinos Vouthounis, Olivera Stojadinovic, Harold Brem, Mark Im, Marjana Tomic-Canic
Wound healing in its complexity depends on the concerted activity of many signaling pathways. Here, we analyzed how the simultaneous presence of glucocorticoids (GC), retinoic acid (RA) and epidermal growth factor (EGF) affect wound healing at the molecular, cellular and tissue levels. We found that GC inhibit wound healing by inhibiting keratinocyte migration, whereas RA does not. Furthermore, GC block EGF-mediated migration, whereas RA does not. On the molecular level, these compounds target expression of one of the earliest markers of wound healing, cytoskeletal components, keratins K6 and K16...
February 4, 2005: Journal of Molecular Biology
Szabolcs Semsey, Michail Y Tolstorukov, Konstantin Virnik, Victor B Zhurkin, Sankar Adhya
The Gal repressosome is a higher-order nucleoprotein complex that represses transcription of the gal operon in Escherichia coli. During the repressosome assembly, a DNA loop is formed by the interaction of two GalR dimers, bound to two spatially separated operators, OE and OI, flanking the gal promoters. Structure-based genetic analysis indicated that GalR homodimers interact directly and form a V-shaped stacked tetramer in repressosome, further stabilized by HU binding to an architecturally critical position on the DNA...
August 1, 2004: Genes & Development
Aaron R Osborne, Hongquan Zhang, Gyorgy Fejer, Kimberly M Palubin, Melissa I Niesen, George Blanck
The cell surface HLA-DR molecule binds foreign peptide antigen and forms an intercellular complex with the T cell receptor in the course of the development of an immune response against or immune tolerance to the antigen represented by the bound peptide. The HLA-DR molecule also functions as a receptor that mediates cell signaling pathways, including as yet poorly characterized pathway(s) leading to apoptosis. Expression of HLA-DR mRNA and protein is ordinarily inducible by interferon-gamma but is not inducible in tumor cells defective for the retinoblastoma tumor suppressor protein (Rb)...
July 9, 2004: Journal of Biological Chemistry
Konstantin Virnik, Yuri L Lyubchenko, Mikhail A Karymov, Paul Dahlgren, Michael Y Tolstorukov, Szabolcs Semsey, Victor B Zhurkin, Sankar Adhya
DNA looping is often involved in positive and negative regulation of gene transcription in both prokaryotes and eukaryotes. The transcription of the gal operon of Escherichia coli from two overlapping promoters P1 and P2 is negatively regulated via Gal repressosome assembly. It involves binding of two dimeric Gal repressor proteins (GalR) to two operators, O(E) and O(I), flanking the two promoters, and formation of 113 bp DNA loop due to tetramerization of the two bound GalR dimers. The process requires negatively supercoiled DNA and the presence of the histone-like protein HU...
November 14, 2003: Journal of Molecular Biology
P M Gowri, J H Yu, A Shaufl, M A Sperling, R K Menon
The growth hormone (GH)-GH receptor (GHR) axis modulates growth and metabolism and contributes to complications of diabetes mellitus. We analyzed the promoter region of the dominant transcript (L2) of the murine GHR to determine that a cis element, L2C1, interacts with transcription factors NF-Y, BTEB1, and HMG-Y/I. These proteins individually repress GHR expression and together form a repressosome complex in conjunction with mSin3b. The histone deacetylase inhibitor trichostatin A increases expression of the murine GHR gene, enhances association of acetyl-H3 at L2C1, inhibits formation of the repressosome complex, and decreases NF-Y's association with L2C1...
February 2003: Molecular and Cellular Biology
Szabolcs Semsey, Mark Geanacopoulos, Dale E A Lewis, Sankar Adhya
The assembly of the Gal repressosome, a higher order nucleoprotein complex that represses transcription of the gal operon in Escherichia coli, involves the formation of a DNA loop encompassing the promoter segment. GalR dimers bound to two spatially separated operators, O(E) and O(I), specifically interact with the histone-like protein HU and close the loop in supercoiled DNA. We isolated and characterized a GalR mutant containing an amino acid substitution (R282L) that can repress transcription in the absence of HU and supercoiled DNA both in vivo and in vitro...
August 15, 2002: EMBO Journal
Mark Geanacopoulos, Sankar Adhya
The Gal repressosome is a nucleoprotein complex consisting of 2 GalR dimers, 1 HU, and 1 DNA loop, which represses the transcription of the gal operon. We have adopted a structure-based genetic approach to complement ongoing physical studies of the complex. Homology-based and subsequent alanine-scanning mutageneses suggest that five residues in the DNA-distal subdomain of GalR dimer are important for repressosome formation. A further analysis of these and intragenic suppressors of looping-defective GalR mutants as well as gain-of-function mutants that permit repressosome assembly in the absence of HU show that GalR dimers contact each other in the repressosome in a partially stacked configuration...
September 6, 2002: Journal of Biological Chemistry
S Kar, S Adhya
In Gal repressosome assembly, a DNA loop is formed by the interaction of two GalR, bound to two distal operators, and the binding of the histone-like protein, HU, to an architecturally critical position on DNA to facilitate the GalR-GalR interaction. We show that GalR piggybacks HU to the critical position on the DNA through a specific GalR-HU interaction. This is the first example of HU making a specific contact with another protein. The GalR-HU contact that results in cooperative binding of the two proteins to DNA may be transient and absent in the final repressosome structure...
September 1, 2001: Genes & Development
M Geanacopoulos, G Vasmatzis, V B Zhurkin, S Adhya
Gal repressosome assembly and repression of the gal operon in Escherichia coli occurs when two dimeric GalR proteins and the histone-like HU protein bind to cognate sites causing DNA looping. Structure-based genetic analysis defined the GalR surfaces interacting to form a stacked, V-shaped, tetrameric structure. Stereochemical models of the four possible DNA loops compatible with the GalR tetramer configuration were constructed using the sequence-dependent structural parameters of the interoperator DNA and conformation changes caused by GalR and asymmetric HU binding...
May 2001: Nature Structural Biology
E Ukiyama, A Jancso-Radek, B Li, L Milos, W Zhang, N B Phillips, N Morikawa, C Y King, G Chan, C M Haqq, J T Radek, F Poulat, P K Donahoe, M A Weiss
Protein-directed DNA bending is proposed to regulate assembly of higher-order DNA-multiprotein complexes (enhanceosomes and repressosomes). Because transcriptional initiation is a nonequilibrium process, gene expression may be modulated by the lifetime of such complexes. The human testis-determining factor SRY contains a specific DNA-bending motif, the high-mobility group (HMG) box, and is thus proposed to function as an architectural factor. Here, we test the hypothesis that the kinetic stability of a bent HMG box-DNA complex can in itself modulate transcriptional potency...
March 2001: Molecular Endocrinology
S Adhya, M Geanacopoulos, D E Lewis, S Roy, T Aki
The original model of repression of transcription initiation is steric interference of RNA polymerase binding to a promoter by its repressor protein bound to a DNA site that overlaps the promoter. From the results described here, we propose two other mechanisms of repressor action, both of which involve formation of higher-order DNA-multiprotein complexes. These models also explain the problem of RNA polymerase gaining access to a promoter in the condensed nucleoid in response to an inducing signal to initiate transcription...
1998: Cold Spring Harbor Symposia on Quantitative Biology
M Geanacopoulos, G Vasmatzis, D E Lewis, S Roy, B Lee, S Adhya
Transcription repression of the galactose operon of Escherichia coli requires (1) the binding of the GalR repressor to tandem operators flanking the promoters, (2) the binding of histone-like protein, HU, to a site between the GalR-binding sites, and (3) negatively supercoiled DNA. Under these conditions, protein-protein interactions mediate the formation of a nucleoprotein complex in the form of a DNA loop, which we have termed a repressosome. To analyze the structure of the repressosome, we have screened and isolated galR mutants in which single amino acid substitutions in GalR lead to defects in loop formation while the protein's operator-binding activity is retained...
May 15, 1999: Genes & Development
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