Department of Immunology, Tokai University School of Medicine, Isehara, Kanagawa, Japan.
Institute of Medical Sciences, Tokai University, Isehara, Kanagawa, Japan.
J Exp Med. 2021 Aug 2;218(8). doi: 10.1084/jem.20202648. Epub 2021 Jun 28.
PU.1 (encoded by Spi1), an ETS-family transcription factor with many hematopoietic roles, is highly expressed in the earliest intrathymic T cell progenitors but must be down-regulated during T lineage commitment. The transcription factors Runx1 and GATA3 have been implicated in this Spi1 repression, but the basis of the timing was unknown. We show that increasing Runx1 and/or GATA3 down-regulates Spi1 expression in pro-T cells, while deletion of these factors after Spi1 down-regulation reactivates its expression. Leveraging the stage specificities of repression and transcription factor binding revealed an unconventional but functional site in Spi1 intron 2. Acute Cas9-mediated deletion or disruption of the Runx and GATA motifs in this element reactivates silenced Spi1 expression in a pro-T cell line, substantially more than disruption of other candidate elements, and counteracts the repression of Spi1 in primary pro-T cells during commitment. Thus, Runx1 and GATA3 work stage specifically through an intronic silencing element in mouse Spi1 to control strength and maintenance of Spi1 repression during T lineage commitment.
PU.1（由 Spi1 编码）是一种 ETS 家族转录因子，具有许多造血作用，在最早的胸腺内 T 细胞祖细胞中高度表达，但在 T 细胞谱系分化过程中必须下调。转录因子 Runx1 和 GATA3 已被牵连到 Spi1 的这种抑制中，但时机的基础尚不清楚。我们表明，增加 Runx1 和/或 GATA3 会在原 T 细胞中下调 Spi1 的表达，而在 Spi1 下调后删除这些因子会重新激活其表达。利用抑制和转录因子结合的阶段特异性揭示了 Spi1 内含子 2 中的一个非传统但功能的位点。急性 Cas9 介导的删除或破坏该元件中的 Runx 和 GATA 基序可在原 T 细胞系中重新激活沉默的 Spi1 表达，比破坏其他候选元件的效果显著得多，并抵消了在原代原 T 细胞分化过程中 Spi1 的抑制作用。因此，Runx1 和 GATA3 通过小鼠 Spi1 中的内含子沉默元件在特定阶段发挥作用，以控制 T 细胞谱系分化过程中 Spi1 抑制的强度和维持。
