Newcastle Fibrosis Research Group, Institute of Cellular Medicine, Newcastle University, UK.
Health Research Institute, University of Limerick, Ireland.
Biochim Biophys Acta Gene Regul Mech. 2018 Oct;1861(10):962-970. doi: 10.1016/j.bbagrm.2018.09.001. Epub 2018 Sep 10.
The NF-?B p50 subunit is an important regulator of inflammation, with recent experimental evidence to support it also having a tumor suppressor role. Classically, p50 functions in heterodimeric form with the RelA (p65) NF-?B subunit to activate inflammatory genes. However, p50 also forms homodimers which actively repress NF-?B-dependent inflammatory gene expression and exert an important brake on the inflammatory process. This repressive activity of p50:p50 is thought to be in part mediated by an interaction with the epigenetic repressor protein Histone Deacetylase 1 (HDAC1). However, neither the interaction of p50 with HDAC1 nor the requirement of HDAC1 for the repressive activities of p50 has been well defined. Here we employed in silico prediction with in vitro assays to map sites of interaction of HDAC1 on the p50 protein. Directed mutagenesis of one such region resulted in almost complete loss of HDAC1 binding to p50. Transfected mutant p50 protein lacking the putative HDAC1 docking motif resulted in enhanced cytokine and chemokine expression when compared with cells expressing a transfected wild type p50. In addition, expression of this mutant p50 was associated with enhanced chemoattraction of neutrophils and acetylation of known inflammatory genes demonstrating the likely importance of the p50:HDAC1 interaction for controlling inflammation. These new insights provide an advance on current knowledge of the mechanisms by which NF-?B-dependent gene transcription are regulated and highlight the potential for manipulation of p50:HDAC1 interactions to bring about experimental modulation of chronic inflammation and pathologies associated with dysregulated neutrophil accumulation and activation.
NF-?B p50 亚基是炎症的重要调节剂，最近的实验证据支持其也具有肿瘤抑制作用。经典地，p50 与 RelA（p65）NF-?B 亚基以异二聚体的形式发挥作用，激活炎症基因。然而，p50 也形成同源二聚体，主动抑制 NF-?B 依赖性炎症基因表达，并对炎症过程施加重要的制动。p50:p50 的这种抑制活性部分被认为是通过与表观遗传抑制剂蛋白组蛋白去乙酰化酶 1（HDAC1）相互作用介导的。然而，p50 与 HDAC1 的相互作用以及 HDAC1 对 p50 抑制活性的要求都没有得到很好的定义。在这里，我们使用体外测定的计算预测来绘制 HDAC1 在 p50 蛋白上的相互作用位点。对其中一个区域进行定向突变，导致 HDAC1 与 p50 的结合几乎完全丧失。与表达转染野生型 p50 的细胞相比，缺乏假定的 HDAC1 对接模体的转染突变体 p50 蛋白导致细胞因子和趋化因子表达增强。此外，这种突变体 p50 的表达与已知炎症基因的乙酰化和中性粒细胞的趋化吸引力增强相关，这表明 p50:HDAC1 相互作用对控制炎症可能很重要。这些新的见解为 NF-?B 依赖性基因转录的调控机制提供了新的认识，并强调了操纵 p50:HDAC1 相互作用以实现对慢性炎症和与中性粒细胞积累和激活失调相关的病理的实验调节的潜力。
