N6-methyladenosine (m6A), one of the most chemical modifications, is highly detected in eukaryotic messenger RNA (mRNA). m6A modification is mainly catalyzed by m6A methyltransferase, removed by m6A demethylase, and recognized by m6A binding protein. m6A RNA modification is widely involved in the regulation of mRNA splicing, processing, translation and degradation in all stages of the life cycle. It is related to obesity, tumor, and other diseases. Recently, it has been found that abnormal expression of m6A-related proteins (METTL3/14, WTAP, FTO, ALKBH5, YTHDFs) in tumors can lead to the imbalance of m6A methylation. The oncogenes and tumor suppressors are involved in the occurrence and development of tumors, and are closely related to the prognosis of patients. With the rapid development of RNA immunoprecipitation sequencing technology, high-throughput sequencing technology, liquid chromatography and other detection technologies, the role of m6A in the occurrence and development of tumors has been further uncovered, and targeting m6A has become a new direction of tumor treatment. This paper focuses on the role and mechanism of m6A RNA methylation related factors in the development of cancer and summarized the latest development of m6A RNA methylation detection technology, including the application of demethylase inhibitors such as Rhein, meclofenamic acid2 (MA2), and R-2-hydroxyglutarate (R-2HG). This paper also reviewed the existing literature in tumor targeting therapy and provided summary in tumor prevention and potential treatment with m6A RNA methylation.

So far, researchers have found more than one hundred different kinds of chemical modifications on RNA. Most of these modifications are distributed on high abundant non-coding RNAs and are important for maintaining the functions of these non-coding RNAs. In recent years, thanks to the application of highresolution mass spectrometry and the development of whole-transcriptome sequencing technologies, more and more modifications on mRNA have been discovered, and accurately mapped and localized, including N6-methyladenosine (m6A), N6,2-O-Dimethyladenosine (m6Am), 5-methylcytosine (m5C), inosine (I), pseudouridine (Ψ), N1-methyladenine (m1A), 2′-O-methylation (Nm), N4-acetylcytosine (ac4C) and N7-methylguanine (m7G), etc. Among them, m6A is the most abundant internal modification in eukaryotic mRNA. The identification of its modifying enzymes, recognition proteins, and the discovery of its extensive biological functions have set off an upsurge in the study of ost-transcriptional modifications on mRNA, thus promoting an emerging research field, i.e. Epitranscriptomics. Although our understanding of these reversible and dynamic chemical modifications has just begun to take shape, there is no doubt that a new era of research on genetic information regulation has arrived. This review focuses on the three types of epitranscriptome modifications, namely m6Am, m1A, and pseudouridine—that have been studied by our group. It provides an in-depth introduction to its distribution, function, and high-throughput detection technology, and aims to provide a better understanding of related fields and a window into the flourishing development of the epitranscriptomics.

N6-methyladenosine (m6A) is the most prevalent dynamic and reversible post-transcriptional RNA modification on eukaryote RNA. The enzymes involved in m6A regulation mainly include m6A methyltransferase, demethylase and m6A recognition protein. m6A and related enzymes are involved in the translation, degradation, splicing and transport of mRNA, thus extensively affecting the development, cell differentiation, immunity, metabolism, tumor and other life processes of mammals. However, the role of m6A in skeletal diseases is rarely mentioned. This article summarizes the mechanisms of m6A methyltransferase represented by METTL3 and demethylase represented by FTO in bone marrow mesenchymal stem cells, osteoblasts and osteoclasts during the disease development and progression of osteoporosis. We collated literatures on the effects of METTL3, YTHDF2 and other m6A modifications mediated by several different inflammatory signaling pathways such as mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) in the inflammatory response and their impact on osteoarthritis and rheumatoid arthritis disease progression. The regulatory mechanisms of m6A methylation modification on cytokines and genes such as lymphatic enhancer-binding factor 1 (LEF1) and differentiation-related gene 1 (DRG1) during proliferation and invasion of osteosarcoma are also reviewed. We aim to provide new insights into the pathological mechanisms of various skeletal diseases, and subsequently provide theoretical references for the early diagnosis, clinical treatment and prognosis of diseases.

Circular RNA (circRNA) is a novel RNA with circular structures. It is conserved in various species, and characterized by high stability, high expression levels and tissue specificity. Meanwhile, it could serve as microRNA (miRNA) sponges, bind to RNA-binding proteins, or regulate transcription and protein translation. With the development of high-throughput sequencing and bioinformatics, circRNA was reported to participate in the pathogenesis of cancer. N6-methyladenosine (m6A) modification is the most common type of RNA modification in eukaryote RNA, which is a dynamic and reversible process regulated by m6A methyltransferase, m6A demethylase and m6A-binding proteins. M6A modification is involved in the regulation of RNA nuclear export, splicing, stability, translation and degradation, thus playing a key role in the occurrence and development of multiple human diseases, such as cancers, cardiovascular diseases. Recently, some researches demonstrated that m6A modification of circRNA was essential in the occurrence and development of malignant tumors, such as cervical cancer, colorectal carcinoma, hepatocellular carcinoma, non-small cell lung cancer, poorly differentiated adenocarcinoma of the stomach. In the current manuscript, we summarized the mechanism of m6A RNA modification, the roles of m6A modification in regulation of circRNA, and the effects of circRNA m6A modification on tumor. The potential clinical application value of m6A-modified circRNA was further discussed, as to provide some new ideas and ways for early diagnosis, clinical treatment and prognosis of tumors.

N6-adenosine methylation, a form of methylation of the adenosine N6 site, is often found in eukaryotic mRNA and is one of the most common forms of internal RNA modification. Studies have shown that m6A affects cellular biological processes by regulating gene expression; also the regulators of m6A play a key role in the occurrence and development of various cancers. Prostate Cancer (PCa) is a common malignant tumor in men, and the risk of the disease in men over 60 years of age is increasing year by year. With the aging population, the number of PCa can be expected to continue to rise. In recent years, the role of m6A in tumorigenesis has received widespread attention, but studies on m6A methylation modification in PCa are still limited; therefore, it is particularly important to further explore the relationship between m6A methylation and PCa. In this paper, we review the recent research progress on the role, mechanism, and application of m6A methylation modification in PCa, especially the detailed review of the mechanism of METTL3, FTO, YTHDF2, three classical m6A-related regulatory proteins in PCa; and the potential application of m6A in advanced PCa (e.g., destructive resistant prostate cancer, bone metastatic prostate cancer). From the perspective of methylation modification, this paper may provide some clues to find effective therapeutic strategies for early diagnosis, treatment, and prognosis of PCa, and more theoretical references to achieve individualized treatment.

RNA 5-methylcytosine (m5C) modification plays an important role in many biological processes, and accurate identification of m5C sites helps to better understand their biological function, so it is necessary to identify the methylation sites of m5C. Although several machine learning methods have been developed to identify the methylation sites of m5C, the ability of prediction remains to be improved. In this paper, we proposed a deep learning algorithm, to predict the methylation site of m5C based on bidirectional short and long-term memory network and attention mechanism. The predicted AUC of m5C was 92.5%, 99.7%, 93.6% and 86.5% for Homo sapiens, Mus musculus, Saccharomyces cerevisiae and Arabidopsis thaliana RNA m5C datasets respectively. Compared with the existing prediction methods, this method has better prediction performance and better generalization ability, which provides a new method for RNA m5C methylation site prediction.