IRF1 supports DNA binding of STAT1 by promoting its phosphorylation
IRF1 supports DNA binding of STAT1 by promoting its phosphorylation
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DOI：
10.1111/imcb.12185
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发表时间：
2018-06
影响因子：
4
通讯作者：
Kosuke Zenke;M. Muroi;K. Tanamoto
中科院分区：
文献类型：
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作者：
Kosuke Zenke;M. Muroi;K. Tanamoto
信号转导和转录激活因子1(STAT1)是Janus激酶(JAK)-STAT信号通路中的关键转录因子，调节包括干扰素调节因子1(IRF1)在内的多种免疫相关基因的表达。在本研究中，我们发现IRF1可以诱导STAT1的磷酸化，进而激活STAT1。当IRF1在HEK293细胞中瞬时表达时，STAT1在Y701处被磷酸化，二聚化，并与含有来自IRF1启动子的伽马激活序列(GAS)的寡核苷酸结合。IRF1的表达还诱导了GAS依赖的启动子报告活性，以及STAT1上游的一种激酶JAK1的磷酸化。虽然没有观察到IRF1和STAT1之间的直接相互作用，但IRF1的反式激活结构域是IRF1介导的STAT1激活所必需的，这表明IRF1调控的基因产物(S)参与了IRF1的激活。此外，表达IRF1的细胞上清液可诱导STAT1和JAK1的磷酸化，以及随后的STAT1与GAS的结合，这一结合不能被干扰素-β或干扰素-γ抗体阻断。在HEK293刺激后，干扰素-γ诱导的STAT1磷酸化持续到30h，但在缺失IRF1的HEK293细胞中磷酸化水平下降。在缺失γ的HEK293细胞中，干扰素-IRF1诱导的IRF1启动子活性也降低，这可以通过与IRF1的互补来挽救。综上所述，这些结果表明IRF1促进了STAT1的DNA结合，进而参与了JAK-STAT信号的正反馈环。
The signal transducer and activator of transcription 1 (STAT1), a pivotal transcription factor in Janus kinase (JAK)–STAT signaling, regulates the expression of a wide range of immune‐related genes, including interferon (IFN) regulatory factor 1 (IRF1). In this study, we found that IRF1 could induce STAT1 phosphorylation and in turn STAT1 activation. When IRF1 was transiently expressed in HEK293 cells, STAT1 phosphorylated at Y701, dimerized and bound to an oligonucleotide containing a gamma‐activated sequence (GAS) derived from the IRF1 promoter. IRF1 expression also induced GAS‐dependent promoter reporter activity, and phosphorylation of JAK1, a kinase upstream of STAT1. Although no direct interaction between IRF1 and STAT1 was observed, the transactivation domain of IRF1 was required for IRF1‐mediated STAT1 activation, indicating the involvement of gene product(s) regulated by IRF1. Moreover, supernatants from cells expressing IRF1 induced phosphorylation of STAT1 and JAK1, and subsequent GAS binding by STAT1 that could not be blocked by treatment with antibodies against IFN‐β or IFN‐γ. IFN‐γ‐induced STAT1 phosphorylation persisted for up to 30 h following stimulation of HEK293, but declined in IRF1‐deficient HEK293 cells. IRF1‐promoter activity induced by IFN‐γ was also reduced in IRF1‐deficient HEK293 cells, which could be rescued by complementation with IRF1. Together these results indicate that IRF1 promotes DNA binding of STAT1, which can in turn participate in a positive feedback loop of JAK–STAT signaling.