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Zeng Z, Chen L, Luo H, Xiao H, Gao S, Zeng Y. Progress on H2B as a multifunctional protein related to pathogens. Life Sci 2024; 347:122654. [PMID: 38657835 DOI: 10.1016/j.lfs.2024.122654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 04/06/2024] [Accepted: 04/21/2024] [Indexed: 04/26/2024]
Abstract
Histone H2B is a member of the core histones, which together with other histones form the nucleosome, the basic structural unit of chromosomes. As scientists delve deeper into histones, researchers gradually realize that histone H2B is not only an important part of nucleosomes, but also plays a momentous role in regulating gene transcription, acting as a receptor and antimicrobial action outside the nucleus. There are a variety of epigenetically modified sites in the H2B tail rich in arginine and lysine, which can occur in ubiquitination, phosphorylation, methylation, acetylation, etc. When stimulated by foreign factors such as bacteria, viruses or parasites, histone H2B can act as a receptor for the recognition of these pathogens, and induce an intrinsic immune response to enhance host defense. In addition, the extrachromosomal histone H2B is also an important anti-microorganism agent, which may be the key to the development of antibiotics in the future. This review aims to summarize the interaction between histone H2B and etiological agents and explore the role of H2B in epigenetic modifications, receptors and antimicrobial activity.
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Affiliation(s)
- Zhuo Zeng
- Institute of Pathogenic Biology, Basic Medicine School, Hengyang Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hengyang City, Hunan Province 421001, PR China
| | - Li Chen
- Institute of Pathogenic Biology, Basic Medicine School, Hengyang Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hengyang City, Hunan Province 421001, PR China
| | - Haodang Luo
- Institute of Pathogenic Biology, Basic Medicine School, Hengyang Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hengyang City, Hunan Province 421001, PR China; The Laboratory Department, The affiliated Nanhua Hospital, University of South China, Hengyang City, Hunan Province 421001, PR China.
| | - Hua Xiao
- Institute of Pathogenic Biology, Basic Medicine School, Hengyang Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hengyang City, Hunan Province 421001, PR China
| | - Siqi Gao
- Institute of Pathogenic Biology, Basic Medicine School, Hengyang Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hengyang City, Hunan Province 421001, PR China
| | - Yanhua Zeng
- Institute of Pathogenic Biology, Basic Medicine School, Hengyang Medical College, University of South China, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hengyang City, Hunan Province 421001, PR China.
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Farrell K, Auerbach A, Musaus M, Navabpour S, Liu C, Lin Y, Xie H, Jarome TJ. Phosphorylation of RPT6 Controls Its Ability to Bind DNA and Regulate Gene Expression in the Hippocampus of Male Rats during Memory Formation. J Neurosci 2024; 44:e1453232023. [PMID: 38124005 PMCID: PMC10860611 DOI: 10.1523/jneurosci.1453-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 10/31/2023] [Accepted: 11/29/2023] [Indexed: 12/23/2023] Open
Abstract
Memory formation requires coordinated control of gene expression, protein synthesis, and ubiquitin-proteasome system (UPS)-mediated protein degradation. The catalytic component of the UPS, the 26S proteasome, contains a 20S catalytic core surrounded by two 19S regulatory caps, and phosphorylation of the 19S cap regulatory subunit RPT6 at serine 120 (pRPT6-S120) has been widely implicated in controlling activity-dependent increases in proteasome activity. Recently, RPT6 was also shown to act outside the proteasome where it has a transcription factor-like role in the hippocampus during memory formation. However, little is known about the proteasome-independent function of "free" RPT6 in the brain or during memory formation and whether phosphorylation of S120 is required for this transcriptional control function. Here, we used RNA-sequencing along with novel genetic approaches and biochemical, molecular, and behavioral assays to test the hypothesis that pRPT6-S120 functions independently of the proteasome to bind DNA and regulate gene expression during memory formation. RNA-sequencing following siRNA-mediated knockdown of free RPT6 revealed 46 gene targets in the dorsal hippocampus of male rats following fear conditioning, where RPT6 was involved in transcriptional activation and repression. Through CRISPR-dCas9-mediated artificial placement of RPT6 at a target gene, we found that RPT6 DNA binding alone may be important for altering gene expression following learning. Further, CRISPR-dCas13-mediated conversion of S120 to glycine on RPT6 revealed that phosphorylation at S120 is necessary for RPT6 to bind DNA and properly regulate transcription during memory formation. Together, we reveal a novel function for phosphorylation of RPT6 in controlling gene transcription during memory formation.
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Affiliation(s)
- Kayla Farrell
- Departments of School of Animal Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
| | - Aubrey Auerbach
- Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
| | - Madeline Musaus
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
| | - Shaghayegh Navabpour
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
| | - Catherine Liu
- Departments of School of Animal Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
| | - Yu Lin
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Blacksburg 24060, Virginia
| | - Hehuang Xie
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Blacksburg 24060, Virginia
- Fralin Life Science Institute at Virginia Tech, Blacksburg 24060, Virginia
| | - Timothy J Jarome
- Departments of School of Animal Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Blacksburg 24060, Virginia
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3
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Maganti N, Moody TD, Truax AD, Thakkar M, Spring AM, Germann MW, Greer SF. Nonproteolytic roles of 19S ATPases in transcription of CIITApIV genes. PLoS One 2014; 9:e91200. [PMID: 24625964 PMCID: PMC3953376 DOI: 10.1371/journal.pone.0091200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 02/11/2014] [Indexed: 11/19/2022] Open
Abstract
Accumulating evidence shows the 26S proteasome is involved in the regulation of gene expression. We and others have demonstrated that proteasome components bind to sites of gene transcription, regulate covalent modifications to histones, and are involved in the assembly of activator complexes in mammalian cells. The mechanisms by which the proteasome influences transcription remain unclear, although prior observations suggest both proteolytic and non-proteolytic activities. Here, we define novel, non-proteolytic, roles for each of the three 19S heterodimers, represented by the 19S ATPases Sug1, S7, and S6a, in mammalian gene expression using the inflammatory gene CIITApIV. These 19S ATPases are recruited to induced CIITApIV promoters and also associate with CIITA coding regions. Additionally, these ATPases interact with elongation factor PTEFb complex members CDK9 and Hexim-1 and with Ser5 phosphorylated RNA Pol II. Both the generation of transcripts from CIITApIV and efficient recruitment of RNA Pol II to CIITApIV are negatively impacted by siRNA mediated knockdown of these 19S ATPases. Together, these results define novel roles for 19S ATPases in mammalian gene expression and indicate roles for these ATPases in promoting transcription processes.
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Affiliation(s)
- Nagini Maganti
- Graduate Program in Cell Biology and Immunology, Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Tomika D. Moody
- Graduate Program in Cell Biology and Immunology, Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Agnieszka D. Truax
- Graduate Program in Cell Biology and Immunology, Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Meghna Thakkar
- Graduate Program in Cell Biology and Immunology, Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Alexander M. Spring
- Department of Chemistry, Georgia State University, Atlanta, Georgia, United States of America
| | - Markus W. Germann
- Department of Chemistry, Georgia State University, Atlanta, Georgia, United States of America
| | - Susanna F. Greer
- Graduate Program in Cell Biology and Immunology, Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
- * E-mail:
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Cks1 enhances transcription efficiency at the GAL1 locus by linking the Paf1 complex to the 19S proteasome. EUKARYOTIC CELL 2013; 12:1192-201. [PMID: 23825181 DOI: 10.1128/ec.00151-13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cks1 was originally identified based on genetic interactions with CDC28, the gene that encodes Cdk1 in the budding yeast Saccharomyces cerevisiae. Subsequent work has shown that Cks1 binds Cdc28 and modulates its activity against certain substrates. However, the Cks1/Cdc28 complex also has a role in transcriptional chromatin remodeling not related to kinase activity. In order to elucidate protein networks associated with Cks1 transcriptional functions, proteomic analysis was performed on immunoaffinity-purified Cks1, identifying a physical interaction with the Paf1 complex. Specifically, we found that the Paf1 complex component Rtf1 interacts directly with Cks1 and that this interaction is essential for efficient recruitment of Cks1 to chromatin in the context of GAL1 gene induction. We further found that Cks1 in this capacity serves as an adaptor allowing Rtf1 to recruit 19S proteasome particles, shown to be required for efficient RNA production from some rapidly inducible genes such as GAL1.
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Abstract
Trinucleotide repeat (TNR) expansion is the causative mutation for at least 17 inherited neurological diseases. An important question in the field is which proteins drive the expansion process. This study reports that the multi-functional protein Sem1 is a novel driver of TNR expansions in budding yeast. Mutants of SEM1 suppress up to 90% of expansions. Subsequent analysis showed that Sem1 facilitates expansions via its function in the 26S proteasome, a highly conserved multi-subunit complex with both proteolytic and non-proteolytic functions. The proteolytic function of the 26S proteasome is relevant to expansions, as mutation of additional proteasome components or treatment of yeast with a proteasome inhibitor suppressed CTG•CAG expansions. The 26S proteasome also drives expansions in human cells. In a human astrocytic cell line, siRNA-mediated knockdown of 26S proteasome subunits PSMC5 or PSMB3 reduced expansions. This expansion phenotype, both in yeast and human cells, is dependent on the proteolytic activity of the proteasome rather than a stress response owing to depletion of free ubiquitin. Thus, the 26S proteasome is a novel factor that drives expansions in both yeast and human cells by a mechanism involving protein degradation.
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Affiliation(s)
- Claire Concannon
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, Galway, Ireland
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Gene expression profile of NFκB repressing factor (NKRF) knockdown cells by microarray analysis. BIOCHIP JOURNAL 2012. [DOI: 10.1007/s13206-012-6307-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Sako K, Maki Y, Kanai T, Kato E, Maekawa S, Yasuda S, Sato T, Watahiki MK, Yamaguchi J. Arabidopsis RPT2a, 19S proteasome subunit, regulates gene silencing via DNA methylation. PLoS One 2012; 7:e37086. [PMID: 22615900 PMCID: PMC3353898 DOI: 10.1371/journal.pone.0037086] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 04/18/2012] [Indexed: 01/03/2023] Open
Abstract
The ubiquitin/proteasome pathway plays a crucial role in many biological processes. Here we report a novel role for the Arabidopsis 19S proteasome subunit RPT2a in regulating gene activity at the transcriptional level via DNA methylation. Knockout mutation of the RPT2a gene did not alter global protein levels; however, the transcriptional activities of reporter transgenes were severely reduced compared to those in the wild type. This transcriptional gene silencing (TGS) was observed for transgenes under control of either the constitutive CaMV 35S promoter or the cold-inducible RD29A promoter. Bisulfite sequencing analysis revealed that both the transgene and endogenous RD29A promoter regions were hypermethylated at CG and non-CG contexts in the rpt2a mutant. Moreover, the TGS of transgenes driven by the CaMV 35S promoters was released by treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine, but not by application of the inhibitor of histone deacetylase Trichostatin A. Genetic crosses with the DNA methyltransferase met1 single or drm1drm2cmt3 triple mutants also resulted in a release of CaMV 35S transgene TGS in the rpt2a mutant background. Increased methylation was also found at transposon sequences, suggesting that the 19S proteasome containing AtRPT2a negatively regulates TGS at transgenes and at specific endogenous genes through DNA methylation.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Junji Yamaguchi
- Faculty of Science and Graduate School of Life Science, Hokkaido University, Sapporo, Japan
- * E-mail:
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Abstract
Regulation of gene transcription is vitally important for the maintenance of normal cellular homeostasis. Failure to correctly regulate gene expression, or to deal with problems that arise during the transcription process, can lead to cellular catastrophe and disease. One of the ways cells cope with the challenges of transcription is by making extensive use of the proteolytic and nonproteolytic activities of the ubiquitin-proteasome system (UPS). Here, we review recent evidence showing deep mechanistic connections between the transcription and ubiquitin-proteasome systems. Our goal is to leave the reader with a sense that just about every step in transcription-from transcription initiation through to export of mRNA from the nucleus-is influenced by the UPS and that all major arms of the system--from the first step in ubiquitin (Ub) conjugation through to the proteasome-are recruited into transcriptional processes to provide regulation, directionality, and deconstructive power.
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Affiliation(s)
- Fuqiang Geng
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8240, USA.
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Dennissen FJA, Kholod N, van Leeuwen FW. The ubiquitin proteasome system in neurodegenerative diseases: culprit, accomplice or victim? Prog Neurobiol 2012; 96:190-207. [PMID: 22270043 DOI: 10.1016/j.pneurobio.2012.01.003] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 12/18/2011] [Accepted: 01/05/2012] [Indexed: 12/14/2022]
Abstract
A shared hallmark for many neurodegenerative disorders is the accumulation of toxic protein species which is assumed to be the cause for these diseases. Since the ubiquitin proteasome system (UPS) is the most important pathway for selective protein degradation it is likely that it is involved in the aetiology neurodegenerative disorders. Indeed, impairment of the UPS has been reported to occur during neurodegeneration. Although accumulation of toxic protein species (amyloid β) are in turn known to impair the UPS the relationship is not necessarily causal. We provide an overview of the most recent insights in the roles the UPS plays in protein degradation and other processes. Additionally, we discuss the role of the UPS in clearance of the toxic proteins known to accumulate in the hallmarks of neurodegenerative diseases. The present paper will focus on critically reviewing the involvement of the UPS in specific neurodegenerative diseases and will discuss if UPS impairment is a cause, a consequence or both of the disease.
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Affiliation(s)
- F J A Dennissen
- Department of Neuroscience, Faculty of Health Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
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Wang D, Zong C, Koag MC, Wang Y, Drews O, Fang C, Scruggs SB, Ping P. Proteome dynamics and proteome function of cardiac 19S proteasomes. Mol Cell Proteomics 2011; 10:M110.006122. [PMID: 21357515 DOI: 10.1074/mcp.m110.006122] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Myocardial proteasomes are comprised of 20S core particles and 19S regulatory particles, which together carry out targeted degradation of cardiac proteins. The 19S complex is unique among the regulators of proteasomes in that it affects both the capacity and specificity of protein degradation. However, a comprehensive molecular characterization of cardiac 19S complexes is lacking. In this investigation, we tailored a multidimensional chromatography-based purification strategy to isolate structurally intact and functionally viable 19S complexes from murine hearts. Two distinct subpopulations of 19S complexes were isolated based upon (1) potency of activating 20S proteolytic activity, and (2) molecular composition using a combination of immuno-detection, two-dimensional-differential gel electrophoresis, and MS-based approaches. Heat shock protein 90 (Hsp90) was identified to be characteristic to 19S subpopulation I. The physical interaction of Hsp90 with 19S complexes was demonstrated via multiple approaches. Inhibition of Hsp90 activity using geldanamycin or BIIB021 potentiated the ability of subpopulation I to activate 20S proteasomes in the murine heart, thus demonstrating functional specificity of Hsp90 in subpopulation I. This investigation has advanced our understanding of the molecular heterogeneity of cardiac proteasomes by identifying molecularly and functionally distinct cardiac 19S complexes. The preferential association of Hsp90 with 19S subpopulation I unveils novel targets for designing proteasome-based therapeutic interventions for combating cardiac disease.
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Affiliation(s)
- Ding Wang
- Department of Physiology and Medicine, Division of Cardiology, University of California at Los Angeles, UCLA School of Medicine, Los Angeles, California 90095, USA
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Bhat KP, Greer SF. Proteolytic and non-proteolytic roles of ubiquitin and the ubiquitin proteasome system in transcriptional regulation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2010; 1809:150-5. [PMID: 21184853 DOI: 10.1016/j.bbagrm.2010.11.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2010] [Revised: 11/29/2010] [Accepted: 11/30/2010] [Indexed: 01/15/2023]
Abstract
The ubiquitin proteasome system (UPS) regulates perhaps the most intriguing balance in all of biology: how cells control protein function and malfunction in order to regulate, and eventually eliminate, the old and error prone while simultaneously synthesizing and orchestrating the new. In light of the growing notion that ubiquitination and the 26S proteasome are central to a multiplicity of diverse cellular functions, we discuss here the proteolytic and non-proteolytic roles of the UPS in regulating pathways ultimately involved in protein synthesis and activity including roles in epigenetics, transcription, and post-translational modifications. This article is part of a Special Issue entitled The 26S Proteasome: When degradation is just not enough!
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Affiliation(s)
- Kavita P Bhat
- Division of Cellular and Molecular Biology and Phsyiclogy, Department of Biology, Georgia State University, Atlanta, GA 30302, USA
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Choi NM, Majumder P, Boss JM. Regulation of major histocompatibility complex class II genes. Curr Opin Immunol 2010; 23:81-7. [PMID: 20970972 DOI: 10.1016/j.coi.2010.09.007] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 09/23/2010] [Indexed: 12/11/2022]
Abstract
The major histocompatibility complex class II (MHC-II) genes are regulated at the level of transcription. Recent studies have shown that chromatin modification is critical for efficient transcription of these genes, and a number of chromatin modifying complexes recruited to MHC-II genes have been described. The MHC-II genes are segregated from each other by a series of chromatin elements, termed MHC-II insulators. Interactions between MHC-insulators and the promoters of MHC-II genes are mediated by the insulator factor CCCTC-binding factor and are critical for efficient expression. This regulatory mechanism provides a novel view of how the entire MHC-II locus is assembled architecturally and can be coordinately controlled.
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Affiliation(s)
- Nancy M Choi
- Department of Microbiology & Immunology, Emory University School of Medicine, 1510 Clifton Road, Atlanta, GA 30322, United States
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Kwak J, Workman JL, Lee D. The proteasome and its regulatory roles in gene expression. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2010; 1809:88-96. [PMID: 20723625 DOI: 10.1016/j.bbagrm.2010.08.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 07/30/2010] [Accepted: 08/07/2010] [Indexed: 12/21/2022]
Abstract
Cumulative evidence indicates that the proteasome, which is mainly known as a protein-degrading machine, is very essential for gene expression. Destructive functions of the proteasome, i.e., ubiquitin-dependent proteolytic activity, are significant for activator localization, activator destruction, co-activator/repressor destruction and PIC disassembly. Non-proteolytic functions of the proteasome are important for recruitment of activators and co-activators to promoters, ubiquitin-dependent histone modification, transcription elongation and possibly maturation of mRNA via the facilitation of mRNA export from the nucleus to the cytoplasm. In this review, we discuss how the proteasome regulates transcription at numerous stages during gene expression. This article is part of a Special Issue entitled The 26S Proteasome: When degradation is just not enough!
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Affiliation(s)
- Jaechan Kwak
- Department of Biological Sciences, KAIST, Yuseong-Gu, Daejeon, 305-701, Korea
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Bhat KP, Truax AD, Brooks JK, Greer SF. Association of the 19S proteasomal ATPases with the ATPase-binding domain of CIITA is essential for CIITA stability and MHC class II expression. Immunol Cell Biol 2010; 88:807-16. [PMID: 20351748 DOI: 10.1038/icb.2010.45] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Major histocompatibility class II (MHC class II) molecules are glycoproteins that present extracellular antigens to CD4(+) T cells and are essential for initiation of adaptive immune responses. MHC class II expression requires recruitment of a master regulator, the class II transactivator (CIITA), to the MHC class II promoter. Others and we have earlier linked CIITA to the ubiquitin-proteasome system by showing that mono-ubiquitination of CIITA increases its transactivity, whereas poly-ubiquitination of CIITA leads to its degradation. We have further shown that the 26S proteasome also has non-proteolytic functions in MHC class II transcription, as 19S ATPase subunits of the 26S proteasome positively regulate MHC class II transcription and are necessary for stable promoter binding of CIITA. Although these basic requirements of the proteasome to initiate MHC class II transcription are known, how CIITA is recruited, stabilized, and degraded remains unclear. Here, we identify a novel N-terminal 19S ATPase-binding domain of CIITA. The ATPase-binding domain lies within the proline/serine/threonine-rich region of CIITA and encompasses a majority of the CIITA degron sequence. Absence of the ATPase-binding domain increases the half-life of CIITA, but blocks MHC class II surface expression, indicating that CIITA requires interaction with the 19S ATPases for both appropriate deployment and destruction.
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Affiliation(s)
- Kavita Purnanda Bhat
- Division of Cellular and Molecular Biology and Physiology, Department of Biology, Georgia State University, Atlanta, GA 30302, USA
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Koues OI, Mehta NT, Truax AD, Dudley RK, Brooks JK, Greer SF. Roles for common MLL/COMPASS subunits and the 19S proteasome in regulating CIITA pIV and MHC class II gene expression and promoter methylation. Epigenetics Chromatin 2010; 3:5. [PMID: 20181089 PMCID: PMC2829561 DOI: 10.1186/1756-8935-3-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 02/04/2010] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Studies indicate that the 19S proteasome contributes to chromatin reorganization, independent of the role the proteasome plays in protein degradation. We have previously shown that components of the 19S proteasome are crucial for regulating inducible histone activation events in mammalian cells. The 19S ATPase Sug1 binds to histone-remodeling enzymes, and in the absence of Sug1, a subset of activating epigenetic modifications including histone H3 acetylation, H3 lysine 4 trimethylation and H3 arginine 17 dimethylation are inhibited at cytokine-inducible major histocompatibilty complex (MHC)-II and class II transactivator (CIITA) promoters, implicating Sug1 in events required to initiate mammalian transcription. RESULTS Our previous studies indicate that H3 lysine 4 trimethylation at cytokine-inducible MHC-II and CIITA promoters is dependent on proteolytic-independent functions of 19S ATPases. In this report, we show that multiple common subunits of the mixed lineage leukemia (MLL)/complex of proteins associated with Set I (COMPASS) complexes bind to the inducible MHC-II and CIITA promoters; that overexpressing a single common MLL/COMPASS subunit significantly enhances promoter activity and MHC-II HLA-DRA expression; and that these common subunits are important for H3 lysine 4 trimethylation at MHC-II and CIITA promoters. In addition, we show that H3 lysine 27 trimethylation, which is inversely correlated with H3 lysine 4 trimethylation, is significantly elevated in the presence of diminished 19S ATPase Sug1. CONCLUSION Taken together, these experiments suggest that the 19S proteasome plays a crucial role in the initial reorganization of events enabling the relaxation of the repressive chromatin structure surrounding inducible promoters.
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Affiliation(s)
- Olivia I Koues
- Division of Cellular and Molecular Biology and Physiology, Georgia State University, Atlanta, Georgia, USA
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The 19S ATPase S6a (S6'/TBP1) regulates the transcription initiation of class II transactivator. J Mol Biol 2009; 395:254-69. [PMID: 19853614 DOI: 10.1016/j.jmb.2009.10.035] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 10/13/2009] [Accepted: 10/14/2009] [Indexed: 01/24/2023]
Abstract
Class II transactivator (CIITA) is the master regulator of the major histocompatibility class II transcription complex (MHC-II) and is critical for initiation of adaptive immune responses. We have previously demonstrated that the 19S proteasome ATPase Sug1 plays a significant role in regulating CIITA activity and MHC-II expression. We now show that an additional component of the 19S complex, the 19S ATPase S6a (S6'/Tat-binding protein 1), is crucial for regulating cytokine-inducible transcription of CIITA. Lack of S6a negatively impacts CIITA activity and CIITA expression. Decreased expression of S6a significantly diminishes the recruitment of transcription factors to the CIITA interferon-gamma-inducible promoter [CIITA promoter IV (pIV)] and significantly decreases CIITApIV histone H3 and histone H4 acetylation, with a preferential loss of acetylation at H3 lysine 18 and H4 lysine 8. In addition, we provide evidence for the involvement of the 19S AAA (ATPases associated with diverse cellular activity) ATPase hexamer as the 19S ATPase S6b binds CIITApIV in an S6a-dependent fashion and has effects similar to S6a on CIITApIV histone acetylation. These analyses demonstrate the importance of 19S ATPases in the assembly of CIITApIV transcription machinery and provide additional insight into the regulatory mechanisms of the 19S proteasome in mammalian transcription.
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