title: The pre-TCR signal induces transcriptional silencing of the TCRγ locus by reducing the recruitment of STAT5 and Runx to transcriptional enhancers.
abstract: The mouse TCRγ locus is positively regulated by the transcription factors STAT5 and Runx. While the locus undergoes frequent rearrangements in T lymphocytes, TCRγ transcription is repressed in αβ T cells. This phenomenon, known as TCRγ silencing, depends on pre-TCR-induced thymocyte proliferation. The molecular basis for TCRγ silencing, however, is largely unknown. Here, we show that pre-TCR signaling reduces transcription and histone acetylation of the TCRγ locus irrespective of V-J rearrangements. We also demonstrate that Runx is recruited to Eγ and HsA enhancer elements of the TCRγ locus, primarily at the CD4(-)CD8(-) double-negative stage and that Runx binding to these elements decreases at later stages of thymocyte development. Importantly, anti-CD3 antibody treatment decreased IL-7R expression levels, STAT5 phosphorylation and recruitment of STAT5 and Runx to Eγ and HsA elements in RAG2-deficient thymocytes, suggesting that pre-TCR signaling triggers reduced binding of STAT5 and Runx to the enhancer elements. Furthermore, we observed that misexpression of STAT5 or Runx in the CD4(+)CD8(+) double-positive cell line DPK induces TCRγ gene transcription. Finally, we showed that TCRγ transcription is induced in αβ T cells from Runx3 transgenic mice, suggesting that Runx3 counteracts TCRγ silencing in αβ T cells in vivo. Our results suggest that pre-TCR signaling indirectly inactivates TCRγ enhancers by reducing recruitment of STAT5 and Runx and imply that this effect is an important step for TCRγ silencing in αβ T cells.
authors.affiliation: Laboratory of Biological Protection, Department of Biological Responses, Institute for Virus Research, Kyoto University, Sakyo-ku, Japan.
authors.forename: Shizue
authors.initials: S
authors.lastname: Tani-Ichi
authors.forename: Masanobu
authors.initials: M
authors.lastname: Satake
authors.forename: Koichi
authors.initials: K
authors.lastname: Ikuta
mesh_terms: D000818:Animals; D050657:Core Binding Factor alpha Subunits / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics; D004742:Enhancer Elements, Genetic / Q000235:genetics; D020868:Gene Silencing / Q000276:immunology; D019675:Genes, T-Cell Receptor gamma; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011485:Protein Binding / Q000235:genetics; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D020395:Receptors, Interleukin-7 / Q000235:genetics; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D060168:Thymocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics; D019076:Transgenes / Q000235:genetics
chemical_list: D050657:Core Binding Factor alpha Subunits; D004268:DNA-Binding Proteins; C499308:Rag2 protein, mouse; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta; D020395:Receptors, Interleukin-7; D050799:STAT5 Transcription Factor