Regulation of somatic hypermutation by higher-order chromatin structure.

Mol Cell

Research Institute of Molecular Pathology (IMP), Campus-Vienna-Biocenter-1, Vienna Biocenter, 1030 Vienna, Austria; Peter Gorer Department of Immunobiology, School of Immunology & Microbial Sciences, King's College London, London SE1 9RT, UK. Electronic address:

Published: July 2025


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Article Abstract

The generation of protective antibodies by somatic hypermutation (SHM) is essential for antibody maturation and adaptive immunity. SHM involves co-transcriptional mutagenesis of immunoglobulin variable (V) regions regulated by enhancers located hundreds of kilobases away. How 3D chromatin topology affects SHM is poorly understood. Here, we measure higher-order interactions on single alleles of the human immunoglobulin heavy-chain locus (IGH) using Tri-C. We find that SHM is underpinned by a multiway hub wherein the V region is proximal to all enhancers. Cohesin-mediated loop extrusion is dispensable for IGH transcription and hub architecture. Transcription and mutagenesis of IGH switch regions, which are necessary for antibody class-switch recombination, create new chromatin loops that can form without cohesin. However, these additional loops do not compromise hub integrity, V region transcription, or SHM. Thus, antibody maturation occurs within a multiway hub accommodating several gene-enhancer loops in which transcription and mutagenesis of different segments occur non-competitively.

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http://dx.doi.org/10.1016/j.molcel.2025.06.003DOI Listing

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