Recombination activating gene (RAG) expression increases as thymocytes transition from the CD4⁻CD8⁻ double-negative (DN) to the CD4⁺CD8⁺ double-positive (DP) stage, but the physiological importance and mechanism of transcriptional up-regulation are unknown. Here, we show that a DP-specific component of the recombination activating genes antisilencer (DPASE) provokes elevated RAG expression in DP thymocytes. Mouse DP thymocytes lacking the DPASE display RAG expression equivalent to that in DN thymocytes, but this supports only a partial Tcra repertoire due to inefficient secondary Vα-Jα rearrangement. These data indicate that RAG up-regulation is required for a replete Tcra repertoire and that RAG expression is fine-tuned during lymphocyte development to meet the requirements of distinct antigen receptor loci. We further show that transcription factor RORγt directs RAG up-regulation in DP thymocytes by binding to the DPASE and that RORγt influences the Tcra repertoire by binding to the Tcra enhancer. These data, together with prior work showing RORγt to control Tcra rearrangement by regulating DP thymocyte proliferation and survival, reveal RORγt to orchestrate multiple pathways that support formation of the Tcra repertoire.

中文翻译：

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RORγt 上调 DP 胸腺细胞中的 RAG 基因表达以扩展 Tcra 库

随着胸腺细胞从 CD4 ⁻ CD8 ⁻双阴性 (DN) 阶段过渡到 CD4 ⁺ CD8 ⁺双阳性 (DP) 阶段，重组激活基因 (RAG) 表达增加，但转录上调的生理重要性和机制尚不清楚。在这里，我们发现重组激活基因抗沉默剂 (DPASE) 的 DP 特异性成分会引起 DP 胸腺细胞中 RAG 表达升高。缺乏 DPASE 的小鼠 DP 胸腺细胞表现出与 DN 胸腺细胞相当的 RAG 表达，但由于二次 Vα-Jα 重排效率低下，这仅支持部分Tcra库。这些数据表明，完整的Tcra库需要 RAG 上调，并且 RAG 表达在淋巴细胞发育过程中进行微调，以满足不同抗原受体基因座的要求。我们进一步表明，转录因子 RORγt 通过与 DPASE 结合来指导 DP 胸腺细胞中 RAG 上调，并且 RORγt通过与Tcra增强子结合来影响Tcra库。这些数据与先前的工作一起显示 RORγt 通过调节 DP 胸腺细胞增殖和存活来控制Tcra重排，揭示 RORγt 协调支持Tcra库形成的多种途径。