Showing papers by "Hediye Erdjument-Bromage published in 2011"
TL;DR: It is demonstrated that engagement of a subset of Toll-like receptors results in the recruitment of mitochondria to macrophage phagosomes and augments mROS production, revealing a novel pathway linking innate immune signalling to mitochondria, implicate mR OS as an important component of antibacterial responses and further establish mitochondria as hubs for innate immune signaling.
Abstract: Reactive oxygen species (ROS) are essential components of the innate immune response against intracellular bacteria and it is thought that professional phagocytes generate ROS primarily via the phagosomal NADPH oxidase machinery. However, recent studies have suggested that mitochondrial ROS (mROS) also contribute to mouse macrophage bactericidal activity, although the mechanisms linking innate immune signalling to mitochondria for mROS generation remain unclear. Here we demonstrate that engagement of a subset of Toll-like receptors (TLR1, TLR2 and TLR4) results in the recruitment of mitochondria to macrophage phagosomes and augments mROS production. This response involves translocation of a TLR signalling adaptor, tumour necrosis factor receptor-associated factor 6 (TRAF6), to mitochondria, where it engages the protein ECSIT (evolutionarily conserved signalling intermediate in Toll pathways), which is implicated in mitochondrial respiratory chain assembly. Interaction with TRAF6 leads to ECSIT ubiquitination and enrichment at the mitochondrial periphery, resulting in increased mitochondrial and cellular ROS generation. ECSIT- and TRAF6-depleted macrophages have decreased levels of TLR-induced ROS and are significantly impaired in their ability to kill intracellular bacteria. Additionally, reducing macrophage mROS levels by expressing catalase in mitochondria results in defective bacterial killing, confirming the role of mROS in bactericidal activity. These results reveal a novel pathway linking innate immune signalling to mitochondria, implicate mROS as an important component of antibacterial responses and further establish mitochondria as hubs for innate immune signalling.
1,200 citations
TL;DR: This work uses PU-H71 affinity capture to design a proteomic approach that, when combined with bioinformatic pathway analysis, identifies dysregulated signaling networks and key oncoproteins in chronic myeloid leukemia and shows that this method can provide global insights into the biology of individual tumors, including primary patient specimens.
Abstract: Most cancers are characterized by multiple molecular alterations, but identification of the key proteins involved in these signaling pathways is currently beyond reach. We show that the inhibitor PU-H71 preferentially targets tumor-enriched Hsp90 complexes and affinity captures Hsp90-dependent oncogenic client proteins. We have used PU-H71 affinity capture to design a proteomic approach that, when combined with bioinformatic pathway analysis, identifies dysregulated signaling networks and key oncoproteins in chronic myeloid leukemia. The identified interactome overlaps with the well-characterized altered proteome in this cancer, indicating that this method can provide global insights into the biology of individual tumors, including primary patient specimens. In addition, we show that this approach can be used to identify previously uncharacterized oncoproteins and mechanisms, potentially leading to new targeted therapies. We further show that the abundance of the PU-H71-enriched Hsp90 species, which is not dictated by Hsp90 expression alone, is predictive of the cell's sensitivity to Hsp90 inhibition.
242 citations
TL;DR: The results thus show that MTERF4 is an important regulator of translation in mammalian mitochondria and directly controls mitochondrial ribosomal biogenesis and translation.
235 citations
TL;DR: It is reported that PRC2 in mouse ES cells contains at least three additional subunits: JARID2, MTF2, and a novel protein denoted esPRC2p48, and critical functions of these subunits in modulating PRC1's activity and gene expression both in ES cells and during somatic cell reprograming are revealed.
Abstract: Polycomb repressive complex two (PRC2) has been implicated in embryonic stem (ES) cell pluripotency; however, the mechanistic roles of this complex are unclear. It was assumed that ES cells contain PRC2 with the same subunit composition as that identified in HeLa cells and Drosophila embryos. Here, we report that PRC2 in mouse ES cells contains at least three additional subunits: JARID2, MTF2, and a novel protein denoted esPRC2p48. JARID2, MTF2, and esPRC2p48 are highly expressed in mouse ES cells compared to differentiated cells. Importantly, knockdowns of JARID2, MTF2, or esPRC2p48 alter the level of PRC2-mediated H3K27 methylation and result in the expression of differentiation-associated genes in ES cells. Interestingly, expression of JARID2, MTF2, and esPRC2p48 together, but not individually, enhances Oct4/Sox2/Klf4-mediated reprogramming of mouse embryonic fibroblasts (MEFs) into induced pluripotent stem cells, whereas knockdown or knockout of JARID2, MTF2, or esPRC2p48 significantly inhibits reprogramming. JARID2, MTF2, and esPRC2p48 modulate H3K27 methylation and facilitate repression of lineage-associated gene expression when transduced into MEFs, and synergistically stimulate the histone methyltransferase activity of PRC2 in vitro. Therefore, these studies identify JARID2, MTF2, and esPRC2p48 as important regulatory subunits of PRC2 in ES cells and reveal critical functions of these subunits in modulating PRC2's activity and gene expression both in ES cells and during somatic cell reprogramming.
146 citations
TL;DR: These findings highlight a PcG/MBT collaboration that attains repressive chromatin without entailing histone lysine methylation marks.
142 citations
TL;DR: The crystal structure of the essential Mediator head module is reported and architectural principles underlying the role of Mediator in the regulation of gene expression are revealed, suggesting that the head module juxtaposes transcription factor IIH and the carboxy-terminal domain of the largest subunit of Pol II, thereby facilitating phosphorylation of the carboxesy- terminal domain ofPol II.
Abstract: The Mediator complex is a large molecular machine linking transcriptional activators and repressors to RNA polymerase II. It contains three subcomplexes, one of which is a seven-subunit head module. Imasaki et al. have solved the crystallographic structure of the Mediator head module from the yeast Saccharomyces cerevisiae. The subunits form a stable assembly with recognizable binding sites for transcription accessory factors and RNA polymerase II. The structure suggests how transcription factor IIH and the polymerase C-terminal domain are aligned to facilitate phosphorylation of the latter. Mediator is a key regulator of eukaryotic transcription1, connecting activators and repressors bound to regulatory DNA elements with RNA polymerase II1,2,3,4 (Pol II). In the yeast Saccharomyces cerevisiae, Mediator comprises 25 subunits with a total mass of more than one megadalton (refs 5, 6) and is organized into three modules, called head, middle/arm and tail7,8,9. Our understanding of Mediator assembly and its role in regulating transcription has been impeded so far by limited structural information. Here we report the crystal structure of the essential Mediator head module (seven subunits, with a mass of 223 kilodaltons) at a resolution of 4.3 angstroms. Our structure reveals three distinct domains, with the integrity of the complex centred on a bundle of ten helices from five different head subunits. An intricate pattern of interactions within this helical bundle ensures the stable assembly of the head subunits and provides the binding sites for general transcription factors and Pol II. Our structural and functional data suggest that the head module juxtaposes transcription factor IIH and the carboxy-terminal domain of the largest subunit of Pol II, thereby facilitating phosphorylation of the carboxy-terminal domain of Pol II. Our results reveal architectural principles underlying the role of Mediator in the regulation of gene expression.
117 citations
TL;DR: The results suggest that SOD1 is an LCS-1–binding protein that may act in concert with mutant proteins, such as EGFR and KRAS, to promote cell growth, providing a therapeutic target for compounds likeLCS-1.
Abstract: We previously described four small molecules that reduced the growth of lung adenocarcinoma cell lines with either epidermal growth factor receptor (EGFR) or KRAS mutations in a high-throughout chemical screen. By combining affinity proteomics and gene expression analysis, we now propose superoxide dismutase 1 (SOD1) as the most likely target of one of these small molecules, referred to as lung cancer screen 1 (LCS-1). siRNAs against SOD1 slowed the growth of LCS-1 sensitive cell lines; conversely, expression of a SOD1 cDNA increased proliferation of H358 cells and reduced sensitivity of these cells to LCS-1. In addition, SOD1 enzymatic activity was inhibited in vitro by LCS-1 and two closely related analogs. These results suggest that SOD1 is an LCS-1–binding protein that may act in concert with mutant proteins, such as EGFR and KRAS, to promote cell growth, providing a therapeutic target for compounds like LCS-1.
116 citations
TL;DR: Findings highlight the role played by BRD7 in PRMT5- and PRC2-induced transcriptional silencing, and indicate that recruitment of specific RDMs and KDMs is required for efficient transcriptional derepression.
Abstract: Histone modification regulates gene expression, and one major regulatory step in this process is the ability of proteins that recognize epigenetic marks to recruit enzymes required to specify transcriptional outcome. Here we show that BRD7 is a component of hSWI-SNF complexes that interacts with PRMT5 and PRC2. Recruitment studies revealed that BRD7 co-localizes with PRMT5 and PRC2 on 'suppressor of tumorigenecity 7' (ST7) and retinoblastoma-like protein 2 (RBL2) promoters in patient-derived B cell lines, and that its association with these target genes correlates with hypermethylation of H3R8, H4R3 and H3K27. Furthermore, inhibition of BRD7 expression reduces PRMT5 and PRC2 recruitment to ST7 and RBL2 promoters; however, only ST7 becomes transcriptionally derepressed. Evaluation of the PRMT5- and PRC2-induced epigenetic marks revealed that while H3(Me(2))R8, H4(Me(2))R3 and H3(Me(3))K27 marks are erased from the ST7 promoter, demethylation of RBL2 promoter histones is incomplete. We also show that the arginine demethylase (RDM) JMJD6, which can erase PRMT5-induced H4R3 methylation, and the H3K27-lysine-specific demethylases, KDM6A/UTX and KDM6B/JMJD3, are differentially recruited to ST7 and RBL2. These findings highlight the role played by BRD7 in PRMT5- and PRC2-induced transcriptional silencing, and indicate that recruitment of specific RDMs and KDMs is required for efficient transcriptional derepression.
93 citations
TL;DR: It is concluded that FADD and TRIM21 together negatively regulate the late IFN-α pathway in response to viral infection.
59 citations
TL;DR: It is proposed that Merlin mediates contact inhibition and suppresses tumorigenesis by translocating to the nucleus to inhibit CRL4DCAF1, a ubiquitin ligase implicated in promoting cell cycle progression and inhibiting growth arrest, apoptosis, and adhesion.
Abstract: Integrin-mediated activation of PAK (p21-activated kinase) causes phosphorylation and inactivation of the FERM (4.1, ezrin, radixin, moesin) domain–containing protein Merlin, which is encoded by the NF2 ( neurofibromatosis type 2 ) tumor suppressor gene. Conversely, cadherin engagement inactivates PAK, thus leading to accumulation of unphosphorylated Merlin. Current models imply that Merlin inhibits cell proliferation by inhibiting mitogenic signaling at or near the plasma membrane. We have recently shown that the unphosphorylated, growth-inhibiting form of Merlin accumulates in the nucleus and binds to the E3 ubiquitin ligase CRL4 DCAF1 to suppress its activity. Depletion of DCAF1 blocks the hyperproliferation caused by inactivation of Merlin. Conversely, expression of a Merlin-insensitive DCAF1 mutant counteracts the antimitogenic effect of Merlin. Expression of Merlin or silencing of DCAF1 in Nf2- deficient cells induce an overlapping, tumor-suppressive program of gene expression. Mutations present in some tumors from NF2 patients disrupt Merlin’s ability to interact with or inhibit CRL4 DCAF1 . Lastly, depletion of DCAF1 inhibits the hyperproliferation of Schwannoma cells isolated from NF2 patients and suppresses the oncogenic potential of Merlin-deficient tumor cell lines. Current studies are aimed at identifying the substrates and mechanism of action of CRL4 DCAF1 and examining its role in NF2-dependent tumorigenesis in mouse models. We propose that Merlin mediates contact inhibition and suppresses tumorigenesis by translocating to the nucleus to inhibit CRL4 DCAF1 .
39 citations
TL;DR: To the knowledge, this work represents the first reported semisynthesis of a receptor tyrosine kinase and provides a potentially general method for producing single-pass membrane proteins for structural and biochemical characterization.