Hierarchical assembly and disassembly of a transcriptionally active RAG locus in CD4+CD8+ thymocytes

J Exp Med. 2019 Jan 7;216(1):231-243. doi: 10.1084/jem.20181402. Epub 2018 Dec 13.

Abstract

Expression of Rag1 and Rag2 is tightly regulated in developing T cells to mediate TCR gene assembly. Here we have investigated the molecular mechanisms governing the assembly and disassembly of a transcriptionally active RAG locus chromatin hub in CD4+CD8+ thymocytes. Rag1 and Rag2 gene expression in CD4+CD8+ thymocytes depends on Rag1 and Rag2 promoter activation by a distant antisilencer element (ASE). We identify GATA3 and E2A as critical regulators of the ASE, and Runx1 and E2A as critical regulators of the Rag1 promoter. We reveal hierarchical assembly of a transcriptionally active chromatin hub containing the ASE and RAG promoters, with Rag2 recruitment and expression dependent on assembly of a functional ASE-Rag1 framework. Finally, we show that signal-dependent down-regulation of RAG gene expression in CD4+CD8+ thymocytes depends on Ikaros and occurs with disassembly of the RAG locus chromatin hub. Our results provide important new insights into the molecular mechanisms that orchestrate RAG gene expression in developing T cells.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • CD4 Antigens / genetics
  • CD4 Antigens / metabolism
  • CD8 Antigens / genetics
  • CD8 Antigens / metabolism
  • DNA-Binding Proteins / biosynthesis*
  • DNA-Binding Proteins / genetics
  • GATA3 Transcription Factor / genetics
  • GATA3 Transcription Factor / metabolism
  • Gene Expression Regulation / physiology*
  • Genetic Loci / physiology*
  • Homeodomain Proteins / biosynthesis*
  • Homeodomain Proteins / genetics
  • Ikaros Transcription Factor / genetics
  • Ikaros Transcription Factor / metabolism
  • Mice
  • Response Elements / physiology
  • Thymocytes / cytology
  • Thymocytes / metabolism*
  • Transcription, Genetic / physiology*

Substances

  • Basic Helix-Loop-Helix Transcription Factors
  • CD4 Antigens
  • CD8 Antigens
  • CD8 antigen, alpha chain
  • DNA-Binding Proteins
  • GATA3 Transcription Factor
  • Gata3 protein, mouse
  • Homeodomain Proteins
  • Rag2 protein, mouse
  • Tcf3 protein, mouse
  • Zfpn1a1 protein, mouse
  • RAG-1 protein
  • Ikaros Transcription Factor