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Immunoglobulin enhancers increase RNA polymerase 2 stalling at somatic hypermutation target sequences [ChIP-Seq]

ABSTRACT: Somatic hypermutation (SHM) drives the genetic diversity of immunoglobulin genes in activated B cells and supports the generation of antibodies with increased affinity for antigen. SHM is targeted to Ig genes by their enhancers (DIVACs; diversification activators) but how the enhancers mediate this activity is unknown. We show that DIVACs that strongly stimulate SHM increase the phosphorylation of RNA polymerase 2 (Pol2) and Pol2 occupancy in the mutating gene with little or no accompanying increase in elongation-competent Pol2 or production of full length transcripts, indicating the accumulation of stalled Pol2. DIVAC-induced stalling is weakly associated with an increase in the detection of single-stranded DNA bubbles in the mutating target gene. We did not find evidence for anti-sense transcription or an association of H3K27ac with DIVAC activity in the mutating gene. These findings argue for a connection between Pol2 stalling and cis-acting targeting elements in the context of SHM and thus define a mechanistic basis for locus-specific targeting of SHM in the genome. Our results suggest that DIVACs make the target gene a suitable platform for AID-mediated mutation without the need for increasing transcriptional output.

ORGANISM(S): Homo sapiens Gallus gallus

PROVIDER: GSE180177 | GEO | 2021/10/22

REPOSITORIES: GEO

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Immunoglobulin enhancers increase RNA polymerase 2 stalling at somatic hypermutation target sequences [GRO-seq]

Project description:Somatic hypermutation (SHM) drives the genetic diversity of immunoglobulin genes in activated B cells and supports the generation of antibodies with increased affinity for antigen. SHM is targeted to Ig genes by their enhancers (DIVACs; diversification activators) but how the enhancers mediate this activity is unknown. We show that DIVACs that strongly stimulate SHM increase the phosphorylation of RNA polymerase 2 (Pol2) and Pol2 occupancy in the mutating gene with little or no accompanying increase in elongation-competent Pol2 or production of full length transcripts, indicating the accumulation of stalled Pol2. DIVAC-induced stalling is weakly associated with an increase in the detection of single-stranded DNA bubbles in the mutating target gene. We did not find evidence for anti-sense transcription or an association of H3K27ac with DIVAC activity in the mutating gene. These findings argue for a connection between Pol2 stalling and cis-acting targeting elements in the context of SHM and thus define a mechanistic basis for locus-specific targeting of SHM in the genome. Our results suggest that DIVACs make the target gene a suitable platform for AID-mediated mutation without the need for increasing transcriptional output.

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Project description:This SuperSeries is composed of the SubSeries listed below.

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