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Manzo SG, Mazouzi A, Leemans C, van Schaik T, Neyazi N, van Ruiten MS, Rowland BD, Brummelkamp TR, van Steensel B. Chromatin protein complexes involved in gene repression in lamina-associated domains. EMBO J 2024:10.1038/s44318-024-00214-1. [PMID: 39322756 DOI: 10.1038/s44318-024-00214-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 08/05/2024] [Accepted: 08/07/2024] [Indexed: 09/27/2024] Open
Abstract
Lamina-associated domains (LADs) are large chromatin regions that are associated with the nuclear lamina (NL) and form a repressive environment for transcription. The molecular players that mediate gene repression in LADs are currently unknown. Here, we performed FACS-based whole-genome genetic screens in human cells using LAD-integrated fluorescent reporters to identify such regulators. Surprisingly, the screen identified very few NL proteins, but revealed roles for dozens of known chromatin regulators. Among these are the negative elongation factor (NELF) complex and interacting factors involved in RNA polymerase pausing, suggesting that regulation of transcription elongation is a mechanism to repress transcription in LADs. Furthermore, the chromatin remodeler complex BAF and the activation complex Mediator can work both as activators and repressors in LADs, depending on the local context and possibly by rewiring heterochromatin. Our data indicate that the fundamental regulators of transcription and chromatin remodeling, rather than interaction with NL proteins, play a major role in transcription regulation within LADs.
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Affiliation(s)
- Stefano G Manzo
- Division of Gene Regulation, Netherlands Cancer Institute, Amsterdam, the Netherlands
- Oncode Institute, Amsterdam, the Netherlands
- Department of Biosciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy
| | - Abdelghani Mazouzi
- Oncode Institute, Amsterdam, the Netherlands
- Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Christ Leemans
- Division of Gene Regulation, Netherlands Cancer Institute, Amsterdam, the Netherlands
- Oncode Institute, Amsterdam, the Netherlands
| | - Tom van Schaik
- Division of Gene Regulation, Netherlands Cancer Institute, Amsterdam, the Netherlands
- Oncode Institute, Amsterdam, the Netherlands
| | - Nadia Neyazi
- Division of Gene Regulation, Netherlands Cancer Institute, Amsterdam, the Netherlands
- Oncode Institute, Amsterdam, the Netherlands
| | - Marjon S van Ruiten
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Benjamin D Rowland
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Thijn R Brummelkamp
- Oncode Institute, Amsterdam, the Netherlands
- Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Bas van Steensel
- Division of Gene Regulation, Netherlands Cancer Institute, Amsterdam, the Netherlands.
- Oncode Institute, Amsterdam, the Netherlands.
- Division of Molecular Genetics, Netherlands Cancer Institute, Amsterdam, the Netherlands.
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Dhankhar M, Guo Z, Kant A, Basir R, Joshi R, Heo SC, Mauck RL, Lakadamyali M, Shenoy VB. Revealing the Biophysics of Lamina-Associated Domain Formation by Integrating Theoretical Modeling and High-Resolution Imaging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.24.600310. [PMID: 38979207 PMCID: PMC11230226 DOI: 10.1101/2024.06.24.600310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
The interactions between chromatin and the nuclear lamina orchestrate cell type-specific gene activity by forming lamina-associated domains (LADs) which preserve cellular characteristics through gene repression. However, unlike the interactions between chromatin segments, the strength of chromatin-lamina interactions and their dependence on cellular environment are not well understood. Here, we develop a theory to predict the size and shape of peripheral heterochromatin domains by considering the energetics of chromatin-chromatin interactions, the affinity between chromatin and the nuclear lamina and the kinetics of methylation and acetylation9in human mesenchymal stem cells (hMSCs). Through the analysis of super-resolution images of peripheral heterochromatin domains using this theoretical framework, we determine the nuclear lamina-wide distribution of chromatin-lamina affinities. We find that the extracted affinity is highly spatially heterogeneous and shows a bimodal distribution, indicating regions along the lamina with strong chromatin binding and those exhibiting vanishing chromatin affinity interspersed with some regions exhibiting a relatively diminished chromatin interactions, in line with the presence of structures such as nuclear pores. Exploring the role of environmental cues on peripheral chromatin, we find that LAD thickness increases when hMSCs are cultured on a softer substrate, in correlation with contractility-dependent translocation of histone deacetylase 3 (HDAC3) from the cytosol to the nucleus. In soft microenvironments, chromatin becomes sequestered at the nuclear lamina, likely due to the interactions of HDAC3 with the chromatin anchoring protein LAP2 β ,increasing chromatin-lamina affinity, as well as elevated levels of the intranuclear histone methylation. Our findings are further corroborated by pharmacological interventions that inhibit contractility, as well as by manipulating methylation levels using epigenetic drugs. Notably, in the context of tendinosis, a chronic condition characterized by collagen degeneration, we observed a similar increase in the thickness of peripheral chromatin akin to that of cells cultured on soft substrates consistent with theoretical predictions. Our findings underscore the pivotal role of the microenvironment in shaping genome organization and highlight its relevance in pathological conditions.
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Bisht S, Mao Y, Easwaran H. Epigenetic dynamics of aging and cancer development: current concepts from studies mapping aging and cancer epigenomes. Curr Opin Oncol 2024; 36:82-92. [PMID: 38441107 PMCID: PMC10939788 DOI: 10.1097/cco.0000000000001020] [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] [Indexed: 03/08/2024]
Abstract
PURPOSE OF REVIEW This review emphasizes the role of epigenetic processes as incidental changes occurring during aging, which, in turn, promote the development of cancer. RECENT FINDINGS Aging is a complex biological process associated with the progressive deterioration of normal physiological functions, making age a significant risk factor for various disorders, including cancer. The increasing longevity of the population has made cancer a global burden, as the risk of developing most cancers increases with age due to the cumulative effect of exposure to environmental carcinogens and DNA replication errors. The classical 'somatic mutation theory' of cancer cause is being challenged by the observation that multiple normal cells harbor cancer driver mutations without resulting in cancer. In this review, we discuss the role of age-associated epigenetic alterations, including DNA methylation, which occur across all cell types and tissues with advancing age. There is an increasing body of evidence linking these changes with cancer risk and prognosis. SUMMARY A better understanding about the epigenetic changes acquired during aging is critical for comprehending the mechanisms leading to the age-associated increase in cancer and for developing novel therapeutic strategies for cancer treatment and prevention.
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Affiliation(s)
- Shilpa Bisht
- Cancer Genetics and Epigenetics, Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Yiqing Mao
- Cancer Genetics and Epigenetics, Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hariharan Easwaran
- Cancer Genetics and Epigenetics, Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Sobo JM, Alagna NS, Sun SX, Wilson KL, Reddy KL. Lamins: The backbone of the nucleocytoskeleton interface. Curr Opin Cell Biol 2024; 86:102313. [PMID: 38262116 DOI: 10.1016/j.ceb.2023.102313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 12/14/2023] [Accepted: 12/15/2023] [Indexed: 01/25/2024]
Abstract
The nuclear lamina (NL) is a crucial component of the inner nuclear membrane (INM) and consists of lamin filaments and associated proteins. Lamins are type V intermediate filament proteins essential for maintaining the integrity and mechanical properties of the nucleus. In human cells, 'B-type' lamins (lamin B1 and lamin B2) are ubiquitously expressed, while 'A-type' lamins (lamin A, lamin C, and minor isoforms) are expressed in a tissue- and development-specific manner. Lamins homopolymerize to form filaments that localize primarily near the INM, but A-type lamins also localize to and function in the nucleoplasm. Lamins play central roles in the assembly, structure, positioning, and mechanics of the nucleus, modulating cell signaling and influencing development, differentiation, and other activities. This review highlights recent findings on the structure and regulation of lamin filaments, providing insights into their multifaceted functions, including their role as "mechanosensors", delving into the emerging significance of lamin filaments as vital links between cytoskeletal and nuclear structures, chromatin organization, and the genome.
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Affiliation(s)
- Joan M Sobo
- Department of Biological Chemistry, Center for Epigenetics, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Nicholas S Alagna
- Department of Biological Chemistry, Center for Epigenetics, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Sean X Sun
- Department of Mechanical Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Katherine L Wilson
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Karen L Reddy
- Department of Biological Chemistry, Center for Epigenetics, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; Sidney Kimmel Comprehensive Cancer Center, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA.
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Fahrenkrog B, Gasser SM. Structure and function of the nuclear envelope and nuclear pores. FEBS Lett 2023; 597:2703-2704. [PMID: 38013590 DOI: 10.1002/1873-3468.14769] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Affiliation(s)
- Birthe Fahrenkrog
- Biozentrum, University of Basel, Spitalstrasse 41, Basel, 4056, Switzerland
| | - Susan M Gasser
- Department of Fundamental Microbiology, University of Lausanne, Switzerland
- ISREC Foundation, Agora Cancer Research Center, Rue du Bugnon 25A, Lausanne, 1005, Switzerland
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