A Barrier-Type Insulator Forms a Boundary between Active and Inactive Chromatin at the Murine TCRβ Locus

摘要: In CD4−CD8− double-negative thymocytes, the murine Tcrb locus is composed of alternating blocks active and inactive chromatin containing gene segments trypsinogen genes, respectively. Although structure appreciated to be critical for regulated recombination expression segments, molecular mechanisms that maintain integrity these differentially domains are not understood. We localized a boundary between by mapping modifications across interval extending from Prss2 (the most 3′ gene) Dβ1. This boundary, located 6 kb upstream Dβ1, characterized transition repressive (histone H3 lysine 9 dimethylation [H3K9me2]) acetylation [H3ac]) marked peak histone 4 (H3K4me2) colocalizes with retroviral long terminal repeat (LTR). Histone retained fails spread past LTR even on alleles lacking enhancer (Eβ) suggesting features may determined local DNA sequence. Notably, we found LTR-containing functions as barrier-type insulator can protect transgene negative chromosomal position effects. propose that, in vivo, heterochromatin, thereby helps Eβ-regulated domain. also identified low-abundance, Eβ-dependent transcripts initiate at border an adjacent interspersed element. speculate this transcription, which extends Dβ, Jβ Cβ play additional role promoting initial opening