AI Article Synopsis
- Chromatin compaction is a key mechanism in gene repression, traditionally believed to limit transcription by reducing chromatin accessibility.
- Using cryo-electron tomography, researchers mapped the 3D structure of chromatin compacted by the Polycomb Repressive Complex 1 (PRC1) and CBX8, revealing that this complex is porous and stabilized by dynamic interactions.
- The findings suggest that PRC1-chromatin condensates are not rigidly compacted, but instead remain dynamic and accessible in differentiated mouse embryonic stem cells, challenging previous assumptions about Polycomb domains.
Article Abstract
The compaction of chromatin is a prevalent paradigm in gene repression. Chromatin compaction is commonly thought to repress transcription by restricting chromatin accessibility. However, the spatial organisation and dynamics of chromatin compacted by gene-repressing factors are unknown. Using cryo-electron tomography, we solved the three-dimensional structure of chromatin condensed by the Polycomb Repressive Complex 1 (PRC1) in a complex with CBX8. PRC1-condensed chromatin is porous and stabilised through multivalent dynamic interactions of PRC1 with chromatin. Mechanistically, positively charged residues on the internally disordered regions (IDRs) of CBX8 mask negative charges on the DNA to stabilize the condensed state of chromatin. Within condensates, PRC1 remains dynamic while maintaining a static chromatin structure. In differentiated mouse embryonic stem cells, CBX8-bound chromatin remains accessible. These findings challenge the idea of rigidly compacted polycomb domains and instead provides a mechanistic framework for dynamic and accessible PRC1-chromatin condensates.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10888862 | PMC |
| http://dx.doi.org/10.1101/2023.05.08.539931 | DOI Listing |
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