Lineage-specific compaction of Tcrb requires a chromatin barrier to protect the function of a long-range tethering element.
Bottom Line: The second element is a chromatin barrier that protects the tether from hyperactive RC chromatin.When the second element is removed, active RC chromatin spreads upstream, forcing the tether to serve as a new barrier.Acquisition of barrier function by the CTCF element disrupts contacts between distal Vβ gene segments and significantly alters Tcrb repertoires.
Affiliation: Department of Pathology and Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110.Show MeSH
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Mentions: The region of interest has several distinguishing characteristics, including a repetitive tract at its 5′ end and a pair of low-intensity CTCF/RAD21-binding sites (Fig. 6 A, bottom). These features are reminiscent of insulators that form boundaries between active and repressive chromatin domains (Wendt et al., 2008). In keeping with this possibility, a gene situated upstream of the putative chromatin barrier, Prss2, is transcriptionally active in ΔPDβ1 thymocytes but is completely silent in the context of WT, ΔminPDβ1, or mEβ alleles (Fig. 7 A). Prss2 activation in ΔPDβ1 thymocytes is mirrored by an acquisition of H3K4me3 at its promoter region (Fig. 7 B).
Affiliation: Department of Pathology and Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110.