Sequential Enhancer Sequestration Dysregulates Recombination Center Formation at the IgH Locus

Area of Science:

• Genetics
• Molecular Biology
• Immunology

Background:

• Immunoglobulin heavy-chain (IgH) gene assembly involves DNA rearrangements of V_H, D_H, and J_H segments.
• Regulatory elements like enhancers and insulators play crucial roles in orchestrating these complex rearrangements.

Purpose of the Study:

• To investigate the role of intergenic control region 1 (IGCR1) and CTCF binding sites in directing enhancer of immunoglobulin heavy-chain (Eμ) activity.
• To elucidate the mechanisms by which Eμ interacts with regulatory elements during IgH gene assembly.

Main Methods:

• Analysis of DNA rearrangements and chromosome conformation in cells lacking IGCR1.
• Investigating protein-protein interactions involving CTCF and YY1.
• Sequential deletion of CTCF binding regions to assess their impact on recombination.

Main Results:

• In the absence of IGCR1, Eμ forms alternative loops with CTCF binding sites near V_H81X, involving YY1 and CTCF.
• This alternate looping distorts the recombination center, alters D_H rearrangements, and disrupts chromosome conformation, favoring proximal V_H81X recombination.
• Deletion of CTCF binding sites on IGCR1-deleted alleles influences recombination of proximal V_H gene segments.

Conclusions:

• Eμ exhibits distinct interactions with IGCR1-associated versus V_H-associated CTCF binding sites.
• Insulator-like elements play distinct roles in directing enhancer activity during IgH gene assembly, influencing recombination outcomes.