Institute of Pharmaceutical Science, School of Cancer and Pharmaceutical Sciences, King's College London, London SE1 9NN, UK.
Breast Cancer Biology, Innovation Hub, School of Cancer and Pharmaceutical Sciences, King's College London, Guy's Cancer Centre, Guy's Hospital, London SE1 9RT, UK.
Int J Oncol. 2021 Nov;59(5). doi: 10.3892/ijo.2021.5276. Epub 2021 Oct 29.
Post‑translational modification of histones serve a crucial role in the control of gene transcription. Trimethylation of lysine 4 on histone 3 is associated with transcription activation. There are currently six known methylases and six known demethylases that can control the methylation status of this site. Lysine demethylase 5B (KDM5B) is one such demethylase, which can repress gene expression. In particular KDM5B has been found to be overexpressed in a number of cancer types, and small‑molecular weight inhibitors of its demethylase activity have been identified. Previous characterisation of knock‑out mice has revealed that this genotype leads to either embryonic or neonatal lethality. However, the ΔA‑T rich interaction domain (ΔARID)‑KDM5B strain of mice, which have the ARID domain and five amino acids within the Jumonji (Jmj)N domain spliced out from KDM5B, remain viable and fertile. In the present study, ΔARID‑KDM5B was found to have no demethylase activity as determined by demethylase assays and by immunofluorescence in transfected Cos‑1 cells. Furthermore, molecular dynamic simulations revealed conformational changes within the ΔARID‑KDM5B structure compared with that in WT‑KDM5B, particularly in the JmjC domain, which is responsible for the catalytic activity of WT‑KDM5B. This supports the experimental data that shows the loss of demethylase activity. Since knock‑out mice show varying degrees of lethality, these data suggest that KDM5B serves a crucial function in development in a manner that is independent of its demethylase activity.
组蛋白的翻译后修饰在基因转录的调控中起着至关重要的作用。组蛋白 3 赖氨酸 4 的三甲基化与转录激活有关。目前有 6 种已知的甲基转移酶和 6 种已知的去甲基化酶可以控制该位点的甲基化状态。赖氨酸去甲基酶 5B（KDM5B）就是这样一种去甲基化酶，可以抑制基因表达。特别是 KDM5B 在许多癌症类型中表达过度，并且已经鉴定出其去甲基酶活性的小分子抑制剂。以前对敲除小鼠的特征描述表明，这种基因型导致胚胎或新生致死。然而，具有 ARID 结构域和 Jumonji（Jmj）N 结构域内的五个氨基酸缺失的 ΔA-T 富含相互作用结构域（ΔARID）-KDM5B 品系的小鼠仍然具有活力和繁殖力。在本研究中，通过去甲基酶测定和转染的 Cos-1 细胞中的免疫荧光，发现 ΔARID-KDM5B 没有去甲基酶活性。此外，分子动力学模拟揭示了与 WT-KDM5B 相比，ΔARID-KDM5B 结构中的构象变化，特别是在 JmjC 结构域中，该结构域负责 WT-KDM5B 的催化活性。这支持了实验数据，表明去甲基酶活性的丧失。由于敲除小鼠表现出不同程度的致死性，这些数据表明 KDM5B 在发育中发挥着至关重要的作用，而与其去甲基酶活性无关。
