The superenhancer binding factor Med1 is broadly required for optimally expressing and hypermutating IgH genes as well as for terminating their expression through locus suicide recombination
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ABSTRACT: Assembly, expression and maturation of the Immunoglobulin heavy (IgH) chain repertoire necessitates long-range 3D-interactions under regulation by the IgH locus Eµ and 3’ regulatory region (3’RR) super-enhancers. In progenitors, Eµ instrumentally supports VDJ recombination notably towards distal VH genes. In mature cells, the 3’RR first boosts the production of membrane-type IgH transcripts. It later attracts Activation-induced cytidine deaminase at three specific locations: VDJ genes undergoing somatic hypermutation (SHM), switch regions undergoing class switch recombination (CSR), and the 3’RR itself during locus suicide recombination (LSR). In plasma cells devoted to abundant Ig secretion, a late long-range effect is to promote high IgH transcription. The Mediator subunit Med1, which binds super-enhancers and has increased activity after phosphorylation by ERK, was previously attributed a role restricted to class-switched cells. We now show its broader impact on IgH expression, both by promoting recombination of distal VH genes in progenitors and by later supporting SHM. Med1-dependence also marks all long-range functions of the 3’RR, including not only intra- but also trans-chromosomal CSR, LSR, optimal BCR expression and the transcriptional boost featured by plasma cells. Altogether, Med1 appears as a major and specific actor of all the long-range tasks effected by the IgH locus super-enhancers beyond transcription.
ORGANISM(S): Mus musculus
PROVIDER: GSE136845 | GEO | 2022/10/20
REPOSITORIES: GEO
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