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Brown JL, Zhang L, Rocha PP, Kassis JA, Sun MA. Polycomb protein binding and looping in the ON transcriptional state. SCIENCE ADVANCES 2024; 10:eadn1837. [PMID: 38657072 PMCID: PMC11042752 DOI: 10.1126/sciadv.adn1837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 03/22/2024] [Indexed: 04/26/2024]
Abstract
Polycomb group (PcG) proteins mediate epigenetic silencing of important developmental genes by modifying histones and compacting chromatin through two major protein complexes, PRC1 and PRC2. These complexes are recruited to DNA by CpG islands (CGIs) in mammals and Polycomb response elements (PREs) in Drosophila. When PcG target genes are turned OFF, PcG proteins bind to PREs or CGIs, and PREs serve as anchors that loop together and stabilize gene silencing. Here, we address which PcG proteins bind to PREs and whether PREs mediate looping when their targets are in the ON transcriptional state. While the binding of most PcG proteins decreases at PREs in the ON state, one PRC1 component, Ph, remains bound. Further, PREs can loop to each other and with presumptive enhancers in the ON state and, like CGIs, may act as tethering elements between promoters and enhancers. Overall, our data suggest that PREs are important looping elements for developmental loci in both the ON and OFF states.
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Affiliation(s)
- J. Lesley Brown
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Liangliang Zhang
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Pedro P. Rocha
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Judith A. Kassis
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ming-an Sun
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
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Brown JL, Zhang L, Rocha PP, Kassis JA, Sun MA. Polycomb protein binding and looping mediated by Polycomb Response Elements in the ON transcriptional state. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.02.565256. [PMID: 38076900 PMCID: PMC10705551 DOI: 10.1101/2023.11.02.565256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Polycomb group proteins (PcG) mediate epigenetic silencing of important developmental genes and other targets. In Drosophila, canonical PcG-target genes contain Polycomb Response Elements (PREs) that recruit PcG protein complexes including PRC2 that trimethylates H3K27 forming large H3K27me3 domains. In the OFF transcriptional state, PREs loop with each other and this looping strengthens silencing. Here we address the question of what PcG proteins bind to PREs when canonical PcG target genes are expressed, and whether PREs loop when these genes are ON. Our data show that the answer to this question is PRE-specific but general conclusions can be made. First, within a PcG-target gene, some regulatory DNA can remain covered with H3K27me3 and PcG proteins remain bound to PREs in these regions. Second, when PREs are within H3K27ac domains, PcG-binding decreases, however, this depends on the protein and PRE. The DNA binding protein GAF, and the PcG protein Ph remain at PREs even when other PcG proteins are greatly depleted. In the ON state, PREs can still loop with each other, but also form loops with presumptive enhancers. These data support the model that, in addition to their role in PcG silencing, PREs can act as "promoter-tethering elements" mediating interactions between promoter proximal PREs and distant enhancers.
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Affiliation(s)
- J. Lesley Brown
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Liangliang Zhang
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Pedro P Rocha
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
- National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Judith A. Kassis
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ming-an Sun
- Institute of Comparative Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
- Joint International Research Laboratory of Important Animal Infectious Diseases and Zoonoses of Jiangsu Higher Education Institutions, Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
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