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Bilal N Sheikh, Donald Metcalf, Anne K Voss, Tim Thomas
Chromatin plays a central role in maintaining hematopoietic stem cells and during their stepwise differentiation. While a large number of histone modifications and chromatin modifying enzymes have been identified, how these act in concert to produce specific phenotypic outcomes remains to be established. MOZ (KAT6A) is a lysine acetyltransferase and enhances transcription at target gene loci. In contrast, the polycomb group protein BMI1 (PCGF4) is part of the transcriptionally repressive PRC1 complex. Despite their opposing effects on transcription, MOZ and BMI1 regulate biological systems in a similar manner...
October 20, 2016: Experimental Hematology
Alessandra Rossi, Karin J Ferrari, Andrea Piunti, SriGanesh Jammula, Fulvio Chiacchiera, Luca Mazzarella, Andrea Scelfo, Pier Giuseppe Pelicci, Diego Pasini
Leukemia is a complex heterogeneous disease often driven by the expression of oncogenic fusion proteins with different molecular and biochemical properties. Whereas several fusion proteins induce leukemogenesis by activating Hox gene expression (Hox-activating fusions), others impinge on different pathways that do not involve the activation of Hox genes (non-Hox-activating fusions). It has been postulated that one of the main oncogenic properties of the HOXA9 transcription factor is its ability to control the expression of the p16/p19 tumor suppressor locus (Cdkn2a), thereby compensating Polycomb-mediated repression, which is dispensable for leukemias induced by Hox-activating fusions...
October 2016: Science Advances
Chao Yu Zhen, Roubina Tatavosian, Thao Ngoc Huynh, Huy Nguyen Duc, Raibatak Das, Marko Kokotovic, Jonathan B Grimm, Luke D Lavis, Jun Lee, Frances J Mejia, Yang Li, Tingting Yao, Xiaojun Ren
The Polycomb PRC1 plays essential roles in development and disease pathogenesis. Targeting of PRC1 to chromatin is thought to be mediated by the Cbx family proteins (Cbx2/4/6/7/8) binding to histone H3 with a K27me3 modification (H3K27me3). Despite this prevailing view, the molecular mechanisms of targeting remain poorly understood. Here, by combining live-cell single-molecule tracking (SMT) and genetic engineering, we reveal that H3K27me3 contributes significantly to the targeting of Cbx7 and Cbx8 to chromatin, but less to Cbx2, Cbx4, and Cbx6...
October 10, 2016: ELife
Simon Hauri, Federico Comoglio, Makiko Seimiya, Moritz Gerstung, Timo Glatter, Klaus Hansen, Ruedi Aebersold, Renato Paro, Matthias Gstaiger, Christian Beisel
Polycomb group (PcG) proteins are major determinants of gene silencing and epigenetic memory in higher eukaryotes. Here, we systematically mapped the human PcG complexome using a robust affinity purification mass spectrometry approach. Our high-density protein interaction network uncovered a diverse range of PcG complexes. Moreover, our analysis identified PcG interactors linking them to the PcG system, thus providing insight into the molecular function of PcG complexes and mechanisms of recruitment to target genes...
October 4, 2016: Cell Reports
Nathan R Rose, Hamish W King, Neil P Blackledge, Nadezda A Fursova, Katherine Ji Ember, Roman Fischer, Benedikt M Kessler, Robert J Klose
Polycomb group (PcG) proteins function as chromatin-based transcriptional repressors that are essential for normal gene regulation during development. However, how these systems function to achieve transcriptional regulation remains very poorly understood. Here, we discover that the histone H2AK119 E3 ubiquitin ligase activity of Polycomb repressive complex 1 (PRC1) is defined by the composition of its catalytic subunits and is highly regulated by RYBP/YAF2-dependent stimulation. In mouse embryonic stem cells, RYBP plays a central role in shaping H2AK119 mono-ubiquitylation at PcG targets and underpins an activity-based communication between PRC1 and Polycomb repressive complex 2 (PRC2) which is required for normal histone H3 lysine 27 trimethylation (H3K27me3)...
October 5, 2016: ELife
Lluis Morey, Luciano Di Croce
PRC1 complexes contain four core subunits: Pcgf, Phc, Ring1, and Cbx proteins. Interestingly, mammalian genomes have several paralogues for each subunit, which are differentially expressed depending on the cell type, differentiation program, and cellular stimuli. Therefore, identification and characterization of the specific architecture of different PRC1 complexes during cellular differentiation are essential to better understand the function and recruitment mechanism of PRC1 complexes. In this chapter we describe several methods to study Polycomb architecture, and identification of novel interactors in both pluripotent and differentiating mouse embryonic stem cells...
2016: Methods in Molecular Biology
Anthony Sanchez, Angelo De Vivo, Nadima Uprety, Jonghwan Kim, Stanley M Stevens, Younghoon Kee
BMI1 is a component of the Polycomb Repressive Complex 1 (PRC1), which plays a key role in maintaining epigenetic silencing during development. BMI1 also participates in gene silencing during DNA damage response, but the precise downstream function of BMI1 in gene silencing is unclear. Here we identified the UBR5 E3 ligase as a downstream factor of BMI1. We found that UBR5 forms damage-inducible nuclear foci in a manner dependent on the PRC1 components BMI1, RNF1 (RING1a), and RNF2 (RING1b). Whereas transcription is repressed at UV-induced lesions on chromatin, depletion of the PRC1 members or UBR5 alone derepressed transcription elongation at these sites, suggesting that UBR5 functions in a linear pathway with PRC1 in inducing gene silencing at lesions...
October 4, 2016: Proceedings of the National Academy of Sciences of the United States of America
Vincent Loubiere, Anna Delest, Aubin Thomas, Boyan Bonev, Bernd Schuettengruber, Satish Sati, Anne-Marie Martinez, Giacomo Cavalli
Polycomb group proteins form two main complexes, PRC2 and PRC1, which generally coregulate their target genes. Here we show that PRC1 components act as neoplastic tumor suppressors independently of PRC2 function. By mapping the distribution of PRC1 components and trimethylation of histone H3 at Lys27 (H3K27me3) across the genome, we identify a large set of genes that acquire PRC1 in the absence of H3K27me3 in Drosophila larval tissues. These genes massively outnumber canonical targets and are mainly involved in the regulation of cell proliferation, signaling and polarity...
September 19, 2016: Nature Genetics
Jing Feng, Donghong Chen, Alexandre Berr, Wen-Hui Shen
Histone H2A monoubiquitination (H2Aub1), catalyzed by Polycomb Repressive Complex 1 (PRC1), is a key epigenetic mark in Polycomb silencing. However, little is known about how H2Aub1 is read to exert downstream physiological functions. The animal ZUOTIN RELATED FACTOR 1 (ZRF1) has been reported to bind H2Aub1 to promote or repress expression of varied target genes. Here we show that the Arabidopsis ZRF1 homologues, AtZRF1a and AtZRF1b, are key regulators of multiple processes during plant growth and development...
September 14, 2016: Plant Physiology
(no author information available yet)
In this issue, we highlight work from Chung and colleagues investigating the nuclear transport of hTERT, and a report on the 4-Å-resolution cryo-EM structure of the PRC1-microtubule complex by Nogales and colleagues. In addition, we feature a paper from Miller and colleagues that describes what the FUS is about in regulating ER-mitochondrial contacts in neurodegenerative disease.
September 2016: FEBS Journal
Zsolt Toth, Bernadett Papp, Kevin Brulois, Youn Jung Choi, Shou-Jiang Gao, Jae U Jung
One of the hallmarks of the latent phase of Kaposi's sarcoma-associated herpesvirus (KSHV) infection is the global repression of lytic viral gene expression. Following de novo KSHV infection, the establishment of latency involves the chromatinization of the incoming viral genomes and recruitment of the host Polycomb repressive complexes (PRC1 and PRC2) to the promoters of lytic genes, which is accompanied by the inhibition of lytic genes. However, the mechanism of how PRCs are recruited to the KSHV episome is still unknown...
September 2016: PLoS Pathogens
Sarah J Wong, Micah D Gearhart, Alexander B Taylor, David R Nanyes, Daniel J Ha, Angela K Robinson, Jason A Artigas, Oliver J Lee, Borries Demeler, P John Hart, Vivian J Bardwell, Chongwoo A Kim
KDM2B recruits H2A-ubiquitinating activity of a non-canonical Polycomb Repression Complex 1 (PRC1.1) to CpG islands, facilitating gene repression. We investigated the molecular basis of recruitment using in vitro assembly assays to identify minimal components, subcomplexes, and domains required for recruitment. A minimal four-component PRC1.1 complex can be assembled by combining two separately isolated subcomplexes: the DNA-binding KDM2B/SKP1 heterodimer and the heterodimer of BCORL1 and PCGF1, a core component of PRC1...
October 4, 2016: Structure
Tatyana G Kahn, Eshagh Dorafshan, Dorothea Schultheis, Aman Zare, Per Stenberg, Ingolf Reim, Vincenzo Pirrotta, Yuri B Schwartz
Polycomb Group (PcG) proteins are epigenetic repressors essential for control of development and cell differentiation. They form multiple complexes of which PRC1 and PRC2 are evolutionary conserved and obligatory for repression. The targeting of PRC1 and PRC2 is poorly understood and was proposed to be hierarchical and involve tri-methylation of histone H3 (H3K27me3) and/or monoubiquitylation of histone H2A (H2AK118ub). Here, we present a strict test of this hypothesis using the Drosophila model. We discover that neither H3K27me3 nor H2AK118ub is required for targeting PRC complexes to Polycomb Response Elements (PREs)...
August 23, 2016: Nucleic Acids Research
Temitope A Adeyeni, Natasha Khatwani, KayKay San, Uthayashanker R Ezekiel
The B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) locus encodes a 37-kD protein that is a key regulatory component of the polycomb regulatory complex 1 (PRC1). When overexpressed in various cancer types, the BMI1 protein induces cell growth and promotes tumor growth in vitro and in vivo. Curcumin, a major phytochemical in turmeric (Curcuma longa), inhibits the proliferation and survival of many types of cancer cells, both in vitro and in vivo, and has been reported to reduce BMI1 expression in breast cancer cells...
August 2016: Physiological Reports
Xiaochuan Tang, Shiyong Xu, Rongyang Li, Hongpeng Zhang, Qing Chen, Wangjun Wu, Honglin Liu
Meiosis is essential for gametogenesis and exhibits sex-specific property during embryonic development. Retinoic acid (RA) signalling initiates germ cell meiosis by activating Stra8 (stimulated by RA gene 8). Although additional factors are involved in regulating the meiotic initiation of germ cells, their regulatory mechanisms are unclear. In this study, we found that Polycomb repressive complex 1 (PRC1) is largely expressed in chicken ovarian germ and somatic cells during early stages of meiosis. We demonstrated that PRC1 regulates Stra8, pluripotent factors and paracrine factors (Notch ligands) leading to a synergistic effect on the suppression of germ cell meiotic initiation...
December 5, 2016: Molecular and Cellular Endocrinology
(no author information available yet)
EZH2 and BCL6 mediate tethering of a noncanonical PRC1-BCOR complex to repress bivalent promoters.
October 2016: Cancer Discovery
Xuewen Li, Fu Yang, Hongyan Chen, Bowen Deng, Xinghua Li, Rongwen Xi
Polycomb and Trithorax group (PcG and TrxG) genes function to regulate gene transcription by maintaining a repressive or active chromatin state, respectively. This antagonistic activity is important for body patterning during embryonic development, but whether this function module has a role in adult tissues is unclear. Here, we report that in the Drosophila ovary, disruption of the Polycomb repressive complex 1 (PRC1), specifically in the supporting escort cells, causes blockage of cystoblast differentiation and germline stem cell-like tumor formation...
October 1, 2016: Development
Veronika Brynychova, Marie Ehrlichova, Viktor Hlavac, Vlasta Nemcova-Furstova, Vaclav Pecha, Jelena Leva, Marketa Trnkova, Marcela Mrhalova, Roman Kodet, David Vrana, Jan Kovar, Radka Vaclavikova, Ivan Gut, Pavel Soucek
Microtubules are vitally important for eukaryotic cell division. Therefore, we evaluated the relevance of mitotic kinesin KIF14, protein-regulating cytokinesis 1 (PRC1), and citron kinase (CIT) for the prognosis of breast carcinoma patients. Transcript levels were assessed by quantitative real-time PCR in tissues from two independent groups of breast carcinoma patients and compared with clinical data. Tissue PRC1 protein levels were estimated using immunoblotting, and the PRC1 tagged haplotype was analyzed in genomic DNA...
August 6, 2016: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Wendy Béguelin, Matt Teater, Micah D Gearhart, María Teresa Calvo Fernández, Rebecca L Goldstein, Mariano G Cárdenas, Katerina Hatzi, Monica Rosen, Hao Shen, Connie M Corcoran, Michelle Y Hamline, Randy D Gascoyne, Ross L Levine, Omar Abdel-Wahab, Jonathan D Licht, Rita Shaknovich, Olivier Elemento, Vivian J Bardwell, Ari M Melnick
The EZH2 histone methyltransferase mediates the humoral immune response and drives lymphomagenesis through formation of bivalent chromatin domains at critical germinal center (GC) B cell promoters. Herein we show that the actions of EZH2 in driving GC formation and lymphoma precursor lesions require site-specific binding by the BCL6 transcriptional repressor and the presence of a non-canonical PRC1-BCOR-CBX8 complex. The chromodomain protein CBX8 is induced in GC B cells, binds to H3K27me3 at bivalent promoters, and is required for stable association of the complex and the resulting histone modifications...
August 8, 2016: Cancer Cell
Bernd B Zeisig, Chi Wai Eric So
Polycomb repressive complexes (PRCs) are key to normal development and are frequently deregulated in human cancer. In this issue of Cancer Cell, Béguelin et al. report a mechanism of non-canonical PRC1 recruitment by BCL6 in collaboration with EZH2-mediated H3K27me3 for establishment of stable repressive complexes in germinal center B cells.
August 8, 2016: Cancer Cell
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