Jeremy M Boss | PubMed Health

PubMed2026

Selective control of HLA-DRB1 and HLA-DQA1 transcription through DR/DQ super enhancer microelements.

MHC-II gene expression requires promoter-proximal and distal organizing elements. A super enhancer located between the HLA-DR and -DQ genes was dissected into five microdomains (regions A-E) to define its mechanism of action. Regions A and B were required for maximal expression of HLA-DQA1. Region A facilitated HLA-DQA1 expression and substituted for region B in its absence, as well as mediating longer-range interactions with distal CTCF sites. Region D modulated HLA-DRB1 through specific 3D chromatin interactions, whereas a local insulator element (XL9) broadly interacted with the SE. Through deletion of HLA-DRB1 proximal-promoter elements, HLA-DQ expression increased by co-opting interactions with region D, indicating that competition between microelements regulates the absolute levels of MHC-II genes. Together, these data define an additional layer of control for MHC-II genes encoded in one of the most polymorphic and disease-associated regions of the human genome.

CP: immunology↗

PubMed2021

The Murine MHC Class II Super Enhancer IA/IE-SE Contains a Functionally Redundant CTCF-Binding Component and a Novel Element Critical for Maximal Expression.

In both humans and mice, CTCF-binding elements form a series of interacting loops across the MHC class II (MHC-II) locus, and CTCF is required for maximal MHC-II gene expression. In humans, a CTCF-bound chromatin insulator termed XL9 and a super enhancer (SE) DR/DQ-SE situated in the intergenic region between HLA-DRB1 and HLA-DQA1 play critical roles in regulating MHC-II expression. In this study, we identify a similar SE, termed IA/IE-SE, located between H2-Eb1 and H2-Aa of the mouse that contains a CTCF site (C15) and a novel region of high histone H3K27 acetylation. A genetic knockout of C15 was created and its role on MHC-II expression tested on immune cells. We found that C15 deletion did not alter MHC-II expression in B cells, macrophages, and macrophages treated with IFN-γ because of functional redundancy of the remaining MHC-II CTCF sites. Surprisingly, embryonic fibroblasts derived from C15-deleted mice failed to induce MHC-II gene expression in response to IFN-γ, suggesting that at least in this developmental lineage, C15 was required. Examination of the three-dimensional interactions with C15 and the H2-Eb1 and H2-Aa promoters identified interactions within the novel region of high histone acetylation within the IA/IE-SE (termed N1) that contains a PU.1 binding site. CRISPR/Cas9 deletion of N1 altered chromatin interactions across the locus and resulted in reduced MHC-II expression. Together, these data demonstrate the functional redundancy of the MHC-II CTCF elements and identify a functionally conserved SE that is critical for maximal expression of MHC-II genes.

Animals↗