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Cohesin-mediated chromosome looping regulates diverse processes, including antigen receptor (AgR) gene assembly by V(D)J recombination. To understand the mechanisms that coordinate genome topologies, we focused on a genetically tractable AgR locus, Tcrb. Cohesin loading and initiation of loop extrusion (LE) from a nearby CTCF-binding element (CBE) required the promoter of the most 5'Vb segment, creating long-range contacts with downstream DJb segments in the recombination center (RC). CBEs flanking the RC have multiple functions: termination of LE originating in the Vb cluster, initiation of LE in the RC, and insulation of enhancer activity. Deletion of the Tcrb super-enhancer abolished LE from the neighboring RC but spared long-range contacts, indicating that unidirectional LE from upstream Vb segments was sufficient. Thus, Vb promoter- or enhancer-dependent cohesin loading initiates LE in opposite directions across the locus to assemble a broad Tcrb repertoire, a finding that has broad implications for genomic architecture and function.
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http://dx.doi.org/10.1016/j.celrep.2025.116133 | DOI Listing |
Cancers (Basel)
August 2025
Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.
High-risk neuroblastoma remains a major clinical challenge, with a five-year survival rate below 50% despite intensive multimodal therapies. MYCN amplification, a hallmark of high-risk disease, drives an aggressive transcriptional program that maintains undifferentiated and proliferative states in neuroblastoma cells. Given its central role in oncogenic transcription, MYCN represents an attractive therapeutic target; however, its undruggable nature has prompted efforts to identify upstream regulators or cofactors that sustain MYCN expression and oncogenic function.
View Article and Find Full Text PDFCell Rep
August 2025
Immunology Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic addr
Cohesin-mediated chromosome looping regulates diverse processes, including antigen receptor (AgR) gene assembly by V(D)J recombination. To understand the mechanisms that coordinate genome topologies, we focused on a genetically tractable AgR locus, Tcrb. Cohesin loading and initiation of loop extrusion (LE) from a nearby CTCF-binding element (CBE) required the promoter of the most 5'Vb segment, creating long-range contacts with downstream DJb segments in the recombination center (RC).
View Article and Find Full Text PDFNat Commun
August 2025
DNA Motors Group, MRC Laboratory of Medical Sciences, Du Cane Road, London, W12 0HS, UK.
Human topoisomerase II alpha (TOP2α) resolves DNA intertwines between sister chromatids during mitosis. How cohesin, an SMC complex that holds sister chromatids, affects TOP2α decatenation is unclear. To addres this, we developed a quadruple-trap optical tweezers assay to create DNA braids and study TOP2α decatenation at the single-molecule level in real-time.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
August 2025
Physical and Theoretical Chemistry, Department of Chemistry, Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin Building, University of Oxford, Oxford OX1 3QU, United Kingdom.
DNA loop extrusion by cohesin has emerged as a critical pathway for chromosome organization. In vitro single-molecule experiments indicate that loop extrusion requires the assembly of a heteropentameric complex consisting of the SMC1/SMC3 heterodimer, STAG1, NIPBL, and the kleisin SCC1. The complexity of the complete extrusion machinery, consisting of multiple subunits, DNA binding sites, and ATPases poses substantial challenges for revealing the underlying biomolecular mechanism.
View Article and Find Full Text PDFHGG Adv
July 2025
GeneDx, LLC, Gaithersburg, MD 20877, USA. Electronic address:
Cohesin is a multiprotein complex that maintains chromosome integrity during cell division. Disruptions in cohesin or its regulators, including CHTF18, can lead to neurodevelopmental and congenital disorders known as cohesinopathies. CHTF18 participates in cohesin loading during DNA replication, but its role in human disease is not understood.
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