Malik Nazma, Vollmer Stefan, Nanda Sambit Kumar, Lopez-Pelaez Marta, Prescott Alan, Gray Nathanael, Cohen Philip
MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, Dow Street, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
Division of Cell Signalling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
Biochem J. 2015 Jun 15;468(3):363-72. doi: 10.1042/BJ20141523. Epub 2015 Apr 20.
PLK (Polo-like kinase) inhibitors, such as BI-2536, have been reported to suppress IFNB (encoding IFNβ, interferon β) gene transcription induced by ligands that activate TLR3 (Toll-like receptor 3) and TLR4. In the present study, we found that BI-2536 is likely to exert this effect by preventing the interaction of the transcription factors IRF3 (interferon-regulatory factor 3) and c-Jun with the IFNB promoter, but without affecting the TBK1 {TANK [TRAF (tumour-necrosis-factor-receptor-associated factor)-associated nuclear factor κB activator]-binding kinase 1}-catalysed phosphorylation of IRF3 at Ser³⁹⁶, the dimerization and nuclear translocation of IRF3 or the phosphorylation of c-Jun and ATF2 (activating transcription factor 2). Although BI-2536 inhibits few other kinases tested, it interacts with BET (bromodomain and extra-terminal) family members and displaces them from acetylated lysine residues on histones. We found that BET inhibitors that do not inhibit PLKs phenocopied the effect of BI-2536 on IFNB gene transcription. Similarly, BET inhibitors blocked the interaction of IRF5 with the IFNB promoter and the secretion of IFNβ induced by TLR7 or TLR9 ligands in the human plasmacytoid dendritic cell line GEN2.2, but without affecting the nuclear translocation of IRF5. We found that the BET family member BRD4 (bromodomain-containing protein 4) was associated with the IFNB promoter and that this interaction was enhanced by TLR3- or TLR4-ligation and prevented by BI-2536 and other BET inhibitors. Our results establish that BET family members are essential for TLR-stimulated IFNB gene transcription by permitting transcription factors to interact with the IFNB promoter. They also show that the interaction of the IFNB promoter with BRD4 is regulated by TLR ligation and that BI-2536 is likely to suppress IFNB gene transcription by targeting BET family members.
据报道，诸如BI-2536之类的PLK（类Polo样激酶）抑制剂可抑制由激活Toll样受体3（TLR3）和TLR4的配体诱导的IFNB（编码干扰素β）基因转录。在本研究中，我们发现BI-2536可能通过阻止转录因子干扰素调节因子3（IRF3）和c-Jun与IFNB启动子的相互作用来发挥这种作用，但不影响TANK结合激酶1（TBK1）催化的IRF3在丝氨酸³⁹⁶处的磷酸化、IRF3的二聚化和核转位，也不影响c-Jun和激活转录因子2（ATF2）的磷酸化。尽管BI-2536仅抑制少数其他测试激酶，但它与含溴结构域和额外末端（BET）家族成员相互作用，并将它们从组蛋白上的乙酰化赖氨酸残基上置换下来。我们发现，不抑制PLK的BET抑制剂模拟了BI-2536对IFNB基因转录的作用。同样，BET抑制剂在人浆细胞样树突状细胞系GEN2.2中阻断了IRF5与IFNB启动子的相互作用以及由TLR7或TLR9配体诱导的IFNβ分泌，但不影响IRF5的核转位。我们发现BET家族成员含溴结构域蛋白4（BRD4）与IFNB启动子相关，并且这种相互作用在TLR3或TLR4连接时增强，而被BI-2536和其他BET抑制剂阻止。我们的结果表明，BET家族成员通过允许转录因子与IFNB启动子相互作用，对于TLR刺激的IFNB基因转录至关重要。它们还表明，IFNB启动子与BRD4的相互作用受TLR连接调节，并且BI-2536可能通过靶向BET家族成员来抑制IFNB基因转录。
