大蒜素通过miR-486-5p/KDM5B轴增加非小细胞肺癌A549细胞放疗敏感性

目的：探讨大蒜素对非小细胞肺癌（NSCLC）A549细胞放射敏感性影响及其作用机制。方法：大蒜素联合X射线处理A549 细胞,采用MTT法检测A549 细胞增殖活力;Transwell实验检测A549 细胞侵袭能力;克隆形成实验检测A549细胞对放射的敏感性;彗星实验评估A549细胞DNA损伤情况;Western blot检测γ-H2AX、Snail、Vimentin蛋白和组蛋白去甲基化转移酶（KDM5B）的表达量。qRT-PCR检测miR-486-5p的表达量。双荧光素酶报告基因验证miR-486-5p与KDM5B的靶向关系。结果：不同浓度（20、40、60 μg/mL）大蒜素干预可显著抑制A549细胞增殖活力（P ＜0.05）和侵袭能力（P ＜0.05）,并上调miR-486-5p在A549细胞中的表达量（P ＜0.05）。40 μg/mL大蒜素可明显上调X射线对A549细胞增殖和侵袭能力的抑制作用（均P ＜0.05）,且加速了A549细胞DNA损伤。机制上,大蒜素通过上调miR-486-5p增强A549细胞对X射线的敏感性,但敲低miR-486-5p可显著下调大蒜素对A549细胞放射增敏作用。此外,miR-486-5p靶向负调控KDM5B的表达。结论：大蒜素可通过抑制A549细胞增殖、侵袭并诱导细胞DNA损伤,进而增强A549细胞对X射线的敏感性,其作用机制是通过上调miR-486-5p靶向抑制KDM5B来实现的。     

m6A甲基化修饰与泌尿系统肿瘤关系的研究进展

RNA N6-甲基腺嘌呤(m6A)甲基化修饰是广泛存在于真核生物中的一种动态可逆的化学修饰,受到甲基转移酶和去甲基化酶的调控,并被m6A结合蛋白识别加工,进而调节RNA的剪切、出核、稳定性以及翻译过程等。在细胞癌变的过程中,m6A修饰可以通过调控肿瘤相关基因的转录后表达来影响多种肿瘤的增殖、浸润和转移等过程,进而调控肿瘤的发生发展。本文就参与m6A甲基化修饰的3种蛋白、m6A甲基化修饰与多种泌尿系统肿瘤关系的研究进展做一综述。     

Histone methyltransferases and demethylases:regulators in balancing osteogenic and adipogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are characterized by their self-renewing capacity and differentiation potential into multiple tissues. Thus, management of the differentiation capacities of MSCs is important for MSC-based regenerative medicine, such as craniofacial bone regeneration, and in new treatments for metabolic bone diseases, such as osteoporosis. In recent years, histone modification has been a growing topic in the field of MSC lineage specification, in which the Su(var)3–9, enhancer-of-zeste, trithorax (SET) domain-containing family and the Jumonji C (JmjC) domain-containing family represent the major histone lysine methyltransferases (KMTs) and histone lysine demethylases (KDMs), respectively. In this review, we summarize the current understanding of the epigenetic mechanisms by which SET domain-containing KMTs and JmjC domain-containing KDMs balance the osteogenic and adipogenic differentiation of MSCs.     

JMJD2B通过ERK-MAPK途径影响人结直肠癌细胞的恶性表型

目的:探讨组蛋白去甲基化酶JMJD2B影响人结直肠癌细胞恶性表型所介导的信号通路?方法:以RNA干扰技术靶向沉默人结直肠癌细胞HCT116和SW480中JMJD2B的表达,采用蛋白质印迹法检测人结直肠癌细胞ERK-MAPK信号通路的变化,并分别采用CCK-8?流式细胞分析检测细胞增殖和细胞周期分布?凋亡情况?结果:转染JMJD2B siRNA能特异性抑制JMJD2B的表达并导致ERK2表达下调,其磷酸化水平也降低,肿瘤细胞发生G2/M或G0/G1期阻滞,细胞凋亡比例增加,增殖显著受抑(P<0.05)?结论:抑制JMJD2B可通过阻断ERK-MAPK信号转导而抑制人结直肠癌细胞的恶性表型?     

Measurement of lysine-specific demethylase-1 activity in the nuclear extracts by flow-injection based time-of-flight mass spectrometry

Lysine-specific demethylase 1 (LSD1/KDM1A), a histone-modifying enzyme, is upregulated in many cancers, especially in neuroblastoma, breast cancer and hepatoma. We have established a simple method to measure LSD1 activity using a synthetic N-terminal 21-mer peptide of histone H3, which is dimethylated at Lys-4 (H3K4me2). After the enzyme reaction, a substrate of H3K4me2 and two demethylated products, H3K4me1 and H3K4me0, were quantitatively determined by flow injection time-of-flight mass spectrometry (FI-TOF/MS). By using recombinant human LSD1, a nonlinear fitting simulation of the data obtained by FI-TOF/MS produced typical consecutive-reaction kinetics. Apparent K_m and k_cat values of hLSD1 for the first and second demethylation reactions were found to be in the range of reported values. Tranylcypromine was shown to inhibit LSD1 activity with an IC₅₀ of 6.9 µM for the first demethylation reaction and 5.8 µM for the second demethylation reaction. The FI-TOF/MS assay revealed that the endogenous LSD1 activity was higher in the nuclear extracts of SH-SY5Y cells than in HeLa or PC-3 cells, and this is in accordance with the immunoblotting data using an anti-LSD1 antibody. A simple, straightforward FI-TOF/MS assay is described to efficiently measure LSD1 activity in the nuclear extracts of cultured cells.