Chromatin loops, which bring two distal loci of the same chromosome into close physical proximity, are the ubiquitous units of the three-dimensional genome. Recent advances in understanding the spatial organisation of chromatin suggest that several distinct mechanisms control chromatin interactions, such as loop extrusion by cohesin complexes, compartmentalisation by phase separation, direct protein-protein interactions and others. Here, we review different types of chromatin loops and highlight the factors and processes involved in their regulation. We discuss how loop extrusion and compartmentalisation shape chromatin interactions and how these two processes can either positively or negatively influence each other.
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http://dx.doi.org/10.1016/j.gde.2024.102194 | DOI Listing |
Genes Dev
January 2025
Oncode Institute, Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), University Medical Center Utrecht, Utrecht 3584 CT, the Netherlands;
Enhancers are tissue-specific regulatory DNA elements that can activate transcription of genes over distance. Their target genes most often are located in the same contact domain-chromosomal entities formed by cohesin DNA loop extrusion and typically flanked by CTCF-bound boundaries. Enhancers shared by multiple unrelated genes are underexplored but may be more common than anticipated.
View Article and Find Full Text PDFSci Adv
January 2025
Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA.
Understanding chromatin organization requires integrating measurements of genome connectivity and physical structure. It is well established that cohesin is essential for TAD and loop connectivity features in Hi-C, but the corresponding change in physical structure has not been studied using electron microscopy. Pairing chromatin scanning transmission electron tomography with multiomic analysis and single-molecule localization microscopy, we study the role of cohesin in regulating the conformationally defined chromatin nanoscopic packing domains.
View Article and Find Full Text PDFNucleic Acids Res
January 2025
Laboratory of Structural and Functional Organization of Chromosomes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., 119334 Moscow, Russia.
Dictyostelium discoideum is a unicellular slime mold, developing into a multicellular fruiting body upon starvation. Development is accompanied by large-scale shifts in gene expression program, but underlying features of chromatin spatial organization remain unknown. Here, we report that the Dictyostelium 3D genome is organized into positionally conserved, largely consecutive, non-hierarchical and weakly insulated loops at the onset of multicellular development.
View Article and Find Full Text PDFSci Rep
January 2025
Department of Biology, Indiana University, 1001 E 3rd Street, Bloomington, IN 47405, USA.
Genome organization is important for DNA replication, gene expression, and chromosome segregation. In bacteria, two large families of proteins, nucleoid-associated proteins (NAPs) and SMC complexes, play important roles in organizing the genome. NAPs are highly abundant DNA-binding proteins that can bend, wrap, bridge, and compact DNA, while SMC complexes load onto the chromosome, translocate on the DNA, and extrude DNA loops.
View Article and Find Full Text PDFCurr Opin Genet Dev
January 2025
School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China; New Cornerstone Science Laboratory, Westlake University, Hangzhou, Zhejiang, China. Electronic address:
Chromosomes in eukaryotic cells undergo compaction at multiple levels and are folded into hierarchical structures to fit into the nucleus with limited dimensions. Three-dimensional genome organization needs to be coordinated with chromosome-templated processes, including DNA replication and gene transcription. As an ATPase molecular machine, the cohesin complex is a major driver of genome folding, which regulates transcription by modulating promoter-enhancer contacts.
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