RNA的m6A修饰与心血管疾病

N~6-甲基腺嘌呤(N6-methyladenosine,m~6A)是存在于多种RNA中的化学修饰方式,最常见于mRNA。RNA的m~6A含量和效应受到甲基转移酶(Writers)、去甲基酶(Erasers)和甲基化阅读蛋白(Readers)的动态调控。与DNA甲基化修饰和组蛋白修饰相似,它们都参与了多种生物学过程,并与多种疾病的发生发展相关。本文先简要综述m~6A修饰的动态过程及生物学功能,然后重点介绍m~6A修饰与心血管疾病关系的研究进展。     

RNA m~6A甲基化修饰对生物学功能调控作用的研究进展

目前发现的RNA表观遗传修饰存在多种方式,如N~6-甲基腺嘌呤(N~6-methyladenosine, m~6A)、N~1-甲基腺嘌呤(N1-methyladenosine, m~1A)、5-甲基胞嘧啶(5-methylcytidine, m5C)和假尿嘧啶核苷(pseudouridine,PD)等。m~6A是最常见的一种修饰,它是由甲基转移酶和去甲基化酶以及结合蛋白所催化的一种动态可逆的修饰方式,具有重要的调控功能,参与多种细胞进程和疾病的病理过程。最近5年,随着RNA检测技术的发展,m~6A修饰的生物学功能探索已成为RNA领域的前沿热点,该文拟对m~6A甲基化修饰的相关蛋白、生物学功能等方面进行简要概述。     

甲基转移酶METTL3与疾病关系

N~6-甲基腺嘌呤(N~6-methyladenosine),即m~6A修饰,普遍存在于各种真核生物中,是真核细胞RNA中最常见的甲基化修饰,占所有RNA甲基化修饰的80%以上。METTL3作为m~6A甲基转移酶复合体的核心催化亚基,可以修饰多种承担重要功能分子的转录本,并由此参与细胞的分化、增殖和发育等重要生命过程。近年有大量研究发现,METTL3与多种疾病的发生、发展密切相关,如肿瘤、神经系统疾病、心血管疾病等。本文重点介绍了METTL3与这些疾病发生、发展关系的研究进展。     

非编码RNA和RNA修饰对细胞多能性与重编程的影响

非编码RNA是指不翻译成蛋白质,以RNA形式行使功能的生物分子。非编码RNA能够在转录与转录后水平调节基因表达,在表观遗传调控中扮演极其重要的角色。除了非编码RNA外,m RNA分子中腺嘌呤第6位氮原子上的甲基化修饰(N~6-methyladenosine,m~6A)也可以在转录后水平调控基因表达。越来越多的研究表明,非编码RNA和m~6A甲基化修饰在干细胞多能性和细胞命运的调控中发挥重要作用。现结合国内外同行的进展,对中国科学院干细胞与再生医学先导专项在非编码RNA和m~6A甲基化修饰对干细胞多能性与细胞重编程影响研究中的部分成果进行介绍。     

m~6A修饰及其对病毒复制过程调控研究进展

N6-甲基腺嘌呤(N~6-methyladenosine, m~6A)修饰是一种在真核生物中普遍存在的RNA修饰方式,在mRNA转运、稳定、翻译等过程中具有重要作用。m~6A修饰在病毒复制周期中扮演不同的角色,病毒的复制和宿主对病毒的免疫反应都受到m~6A甲基化的影响。本文总结了近年来关于m6A修饰方面的分子作用机制及其对病毒复制以及宿主免疫反应的影响相关研究,以期为病毒生命周期中的表观遗传调控研究提供一定的参考。     

m6A RNA甲基化修饰在心血管疾病中的作用

N6-甲基腺嘌呤（N6-methyladenosine, m6A）是发生在腺嘌呤N6位的甲基化修饰,它是真核生物信使RNA(messenger RNA, mRNA)中最丰富的转录后修饰。m6A修饰是由甲基化酶、去甲基化酶以及结合蛋白质共同调控的动态可逆的过程,并且影响mRNA的生命周期各个阶段,包括稳定性、剪接、核输出、翻译和降解。近年来,有研究报道m6A连续动态调节在心血管疾病中发挥着重要的作用,包括动脉粥样硬化、心肌缺血再灌注损伤、心肌肥厚、心力衰竭、高血压以及腹主动脉瘤等。本文主要对m6A RNA甲基化修饰的作用机制及其在心血管疾病中的最新研究进展进行概述,此外,同时介绍了m6A 单核苷酸多态性（m6A-associated single-nucleotide polymorphisms, m6A-SNPs）在心血管疾病中的应用,以期为心血管疾病的预防及治疗提供新的思路和途径。     

动态RNA甲基化修饰及其调控机制研究进展

RNA可以被100余种化学修饰所修饰。这些化学修饰以甲基化为主,广泛分布于各种类型的RNA中,如r RNA、t RNA、sn RNA、sno RNA和m RNA等,其中针对m RNA内部修饰丰度最高的6-甲基腺嘌呤(m~6A)的研究最为深入。m~6A修饰酶(甲基转移酶METTL3/METTL14/WTAP和去甲基化酶ALKBH5与FTO)和结合蛋白YTHDF2、YTHDF1与YTHDC1的发现,证明了RNA甲基化修饰同DNA甲基化修饰一样是动态可逆的,从而将RNA甲基化修饰由微调控机制提升到表观转录组新层次。而候选m~5C修饰甲基转移酶NSUN家族蛋白和去甲基化酶TET蛋白的初步鉴定,丰富了RNA甲基化修饰表观转录组研究内涵。RNA甲基化介导的表观转录组学调控和作用已成为RNA生物学新研究领域。现重点回顾和展望RNA的m~6A和m~5C甲基化修饰特征及其潜在生物学功能。     

METTL3及其在肿瘤中作用的研究进展

甲基转移酶3 (methyltransferase-like 3, METTL3)是m~6A甲基转移酶复合体中的关键蛋白,能够催化RNA上的腺嘌呤(A)第6位氮原子发生甲基化。METTL3介导的m~6A修饰与RNA的剪接、出核、降解和翻译都有着密切联系,并且在肿瘤的发生发展中起着重要作用。该文主要介绍了METTL3的结构,以及其对mRNA翻译的调控,与非编码RNA的相互作用等多种生物学功能在肿瘤发生发展中作用,旨在为基础及临床医学中对m~6A修饰的研究提供新的研究思路和治疗靶点。     

蓬勃发展的表观转录组学

迄今为止,研究者们在 RNA 上已经发现了百余种不同种类的化学修饰,这些修饰大都分布在丰度较高的非编码 RNA中,并对非编码 RNA功能的维持具有重要作用。近年来,得益于高分辨率质谱的应用以及全转录组测序技术的开发,越来越多的 mRNA 上的修饰被发现、精确定量和定位,包括N6-甲基腺嘌呤（m6A）、N6,2-O-二甲基腺嘌呤（m6Am）、5-甲基胞嘧啶（m5C）、 次黄嘌呤（I）、假尿嘧啶（Ψ）、N1-甲基腺嘌呤（m1A）、2′-O-甲基化（Nm）、N4-乙酰胞嘧啶（ac4C）和N7 甲基鸟嘌呤（m7G）等。其中特别是m6A,作为真核生物mRNA中含量最丰富的内部修饰,其修饰酶、识别蛋白质的鉴定以及其广泛的生物学功能的发现,掀起了mRNA上转录后修饰研究的热潮,从而促进了新兴的研究领域——表观转录组学的诞生。尽管我们对这些可逆、动态的化学修饰的理解刚刚开始形成,但毫无疑问,一个关于遗传信息调控研究的新时代已经到来。本综述集中在本课题组关注较多的3种表观转录组修饰即m1A,m6Am和Ψ,从其分布、功能和高通量检测技术等方面进行深入介绍,旨在为相关领域的研究者提供一个了解蓬勃发展的表观转录组学的窗口。     

N6-甲基腺苷修饰（m6A）在乳腺癌中的研究进展

乳腺癌是女性最常见的癌症之一,也是导致女性癌症死亡的最主要原因.尽管早期乳腺癌的治疗已经取得了极大进展,但晚期伴转移乳腺癌治疗效果较差,具有高复发率和高死亡率.因此,鉴定新的用于诊断和预测乳腺癌转移的分子标记、开发新的治疗策略成为迫切需要.近年来,mRNA的异常N~6-甲基腺苷修饰(N~6-methyladenosine,m~6A)对癌基因功能和表达水平的表观遗传学调控逐渐成为恶性乳腺癌研究的焦点.本文分析和总结了m~6A甲基化修饰及其调节蛋白参与调控乳腺癌发生发展的最新研究进展,以期为乳腺癌中m~6A甲基化修饰研究提供新的思路和参考,进一步为乳腺癌的诊断、治疗、预后及监测提供新的有效策略.     

A dynamic reversible RNA N6-methyladenosine modification: current status and perspectives

N⁶-methyladenosine (m⁶A), as the most abundant RNA epigenetic modifications, has been shown to play critical roles in various biological functions. Research about enzymes that can catalyze and remove m⁶A have revealed its comprehensive roles in messenger RNA (mRNA) metabolism and other physiological processes. The “readers” including YTH domain-containing proteins, hnRNPC, hnRNPG, hnRNPA2B1, IGF2BP1, IGF2BP2, and IGF2BP3, which can affect the fates of mRNA in an m⁶A-dependent manner. In this review, we focus on recent advances in the research of the m⁶A modifications, especially about the latest functions of its writers, erasers, readers in RNA metabolism, cancer, and lipid metabolism. In the end, we provide insights into the underlying molecular mechanisms of m⁶A modifications.     

m^6 A RNA甲基化修饰异常在肿瘤中的作用

N6-甲基腺嘌呤(N6-methyladenosine,m6A)是真核生物信使RNA(messenger RNA,mRNA)含量最多的化学修饰之一。m6A修饰主要由m6A甲基转移酶(methyltransferase)催化,m6A去甲基酶(demethylase)去除,并由m6A结合蛋白(binding protein)识别。它广泛参与调控mRNA剪接、加工、翻译和降解等生命周期的各个阶段,且与肥胖和肿瘤等多种疾病及异常的生理功能相关。近年的研究发现,肿瘤中m6A相关蛋白质(METTL3/14、WTAP、FTO、ALKBH5、YTHDFs)的异常表达,引发m6A甲基化的失调,调控致癌基因和抑癌基因的表达参与肿瘤的发生与发展,并与患者预后不良密切相关。随着RNA免疫沉淀测序技术与高通量测序技术和液相色谱等检测技术的快速发展,有关m6A在肿瘤发生发展中的作用机制研究的进展迅猛,靶向m6A也成为肿瘤临床治疗的新方向。本文重点对m6A RNA甲基化相关因子在癌症发生发展中的作用及机制进行综述,总结m6A RNA甲基化检测技术的最新进展,梳理现有文献报道的脱甲基酶抑制剂大黄酸、甲氯芬那酸2(meclofenamic acid2,MA2)和右旋羟戊二酸(R-2-hydroxyglutarate,R-2HG)等在肿瘤靶向治疗中的运用,为以m6A RNA甲基化为切入点的肿瘤防治研究提供思路与理论参考。     

The interplay between m6A modification and non-coding RNA in cancer stemness modulation: mechanisms,signaling pathways,and clinical implications

Cancer stemness, mainly consisting of chemo-resistance, radio-resistance, tumorigenesis, metastasis, tumor self-renewal, cancer metabolism reprogramming, and tumor immuno-microenvironment remodeling, play crucial roles in the cancer progression process and has become the hotspot of cancer research field in recent years. Nowadays, the exact molecular mechanisms of cancer stemness have not been fully understood. Extensive studies have recently implicated that non-coding RNA (ncRNA) plays vital roles in modulating cancer stemness. Notably, N6-methyladenosine (m6A) modification is of crucial importance for RNAs to exert their biological functions, including RNA splicing, stability, translation, degradation, and export. Emerging evidence has revealed that m6A modification can govern the expressions and functions of ncRNAs, consequently controlling cancer stemness properties. However, the interaction mechanisms between ncRNAs and m6A modification in cancer stemness modulation are rarely investigated. In this review, we elucidate the recent findings on the relationships of m6A modification, ncRNAs, and cancer stemness. We also focus on some key signaling pathways such as Wnt/β-catenin signaling, MAPK signaling, Hippo signaling, and JAK/STAT3 signaling to illustrate the underlying interplay mechanisms between m6A modification and ncRNAs in cancer stemness. In particular, we briefly highlight the clinical potential of ncRNAs and m6A modifiers as promising biomarkers and therapeutic targets for indicating cancer stemness properties and improving the diagnostic precision for a wide variety of cancers.     

The functional roles,cross-talk and clinical implications of m6A modification and circRNA in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. HCC has high rates of death and recurrence, as well as very low survival rates. N6-methyladenosine (m6A) is the most abundant modification in eukaryotic RNAs, and circRNAs are a class of circular noncoding RNAs that are generated by back-splicing and they modulate multiple functions in a variety of cellular processes. Although the carcinogenesis of HCC is complex, emerging evidence has indicated that m6A modification and circRNA play vital roles in HCC development and progression. However, the underlying mechanisms governing HCC, their cross-talk, and clinical implications have not been fully elucidated. Therefore, in this paper, we elucidated the biological functions and molecular mechanisms of m6A modification in the carcinogenesis of HCC by illustrating three different regulatory factors ("writer", "eraser", and "reader") of the m6A modification process. Additionally, we dissected the functional roles of circRNAs in various malignant behaviors of HCC, thereby contributing to HCC initiation, progression and relapse. Furthermore, we demonstrated the cross-talk and interplay between m6A modification and circRNA by revealing the effects of the collaboration of circRNA and m6A modification on HCC progression. Finally, we proposed the clinical potential and implications of m6A modifiers and circRNAs as diagnostic biomarkers and therapeutic targets for HCC diagnosis, treatment and prognosis evaluation.     

Methyltransferase-like 3-mediated N6-methyladenosine modification of miR-7212-5p drives osteoblast differentiation and fracture healing

N6-methyladenosine (m6A) modification has been reported in various diseases and implicated in increasing numbers of biological processes. However, previous studies have not focused on the role of m6A modification in fracture healing. Here, we demonstrated that m6A modifications are decreased during fracture healing and that methyltransferase-like 3 (METTL3) is the main factor involved in the abnormal changes in m6A modifications. Down-regulation of METTL3 promotes osteogenic processes both in vitro and in vivo, and this effect is recapitulated by the suppression of miR-7212-5p maturation. Further studies have shown that miR-7212-5p inhibits osteoblast differentiation in MC3T3-E1 cells by targeting FGFR3. The present study demonstrated an important role of the METTL3/miR-7212-5p/FGFR3 axis and provided new insights on m6A modification in fracture healing.     

Identification and characterization of N6-methyladenosine modification of circRNAs in glioblastoma

This research systematically profiled the global N6-methyladenosine modification pattern of circular RNAs (circRNAs) in glioblastoma (GBM). Based on RNA methylation sequencing (MeRIP sequencing or N6-methyladenosine sequencing) and RNA sequencing, we described the N6-methyladenosine modification status and gene expression of circRNAs in GBM and normal brain tissues. N6-methyladenosine–related circRNAs were immunoprecipitated and validated by real-time quantitative PCR. Bioinformatics analysis and related screening were carried out. Compared with those of the NC group, the circRNAs from GBM exhibited 1370 new N6-methyladenosine peaks and 1322 missing N6-methyladenosine peaks. Among the loci associated with altered N6-methyladenosine peaks, 1298 were up-regulated and 1905 were down-regulated. The N6-methyladenosine level tended to be positively correlated with circRNA expression. Bioinformatics analysis was used to predict the biological function of N6-methyladenosine–modified circRNAs and the corresponding signalling pathways. In addition, through PCR validation combined with clinical data mining, we identified five molecules of interest (BUB1, C1S, DTHD1, F13A1 and NDC80) that could be initial candidates for further study of the function and mechanism of N6-methyladenosine–mediated GBM development. In conclusion, our findings demonstrated the N6-methyladenosine modification pattern of circRNAs in human GBM, revealing the possible roles of N6-methyladenosine–mediated novel noncoding RNAs in the origin and progression of GBM.     

Methylation Modifications in Eukaryotic Messenger RNA

RNA methylation modifications have been found for decades of years, which occur at different RNA types of numerous species, and their distribution is species-specific. However, people rarely know their biological functions. There are several identified methylation modifications in eukaryotic messenger RNA （mRNA）, such as NT-methylguanosine （mVG） at the cap, Nr-methyl-2＇-O-methyladenosine （m6Am）, 2＇-O-methylation （Nm） within the cap and the internal positions, and internal N6-methyladenosine （m6A） and 5-methylcytosine （mSC）. Among them, mTG cap was studied more clearly and found to have vital roles in several important mRNA processes like mRNA translation, stability and nuclear export, m6A as the most abundant modification in mRNA was found in the 1970s and has been proposed to function in mRNA splicing, translation, stability, transport and so on. mrA has been discovered as the first RNA reversible modification which is demethylated directly by human fat mass and obesity associated protein （FRO） and its homolog protein, alkylation repair ho- molog 5 （ALKBH5）. b-TO has a special demethylation mechanism that demethylases m6A to A through two over-oxidative intermediate states： N6-hydroxymethyladenosine （hm6A） and Nr-formyladenosine （frA）. The two newly discovered m6A demethylases, bTO and ALKBH5, significantly control energy homeostasis and spermatogenesis, respectively, indicating that the dynamic and reversible mrA, analogous to DNA and histone modifications, plays broad roles in biological kingdoms and brings us an emerging field ＂RNA Epige- netics＂. 5-methylcytosine （5mC） as an epigenetic mark in DNA has been studied widely, but mSC in mRNA is seldom explored. The bisulfide sequencing showed mSC is another abundant modification in mRNA, suggesting that it might be another RNA epigenetic mark. This review focuses on the main methylation modifications in mRNA to describe their formation, distribution, function and demethylation from the current knowledge and to provide future 19erspectives on functional studies.