Fig. 1

Classification of epigenetic modifications. Epigenetic modifications are divided into the following main types. First, DNA methylation modification. DNA methylation modification is mainly regulated by two types enzymes involved, tet methylcytosine dioxygenases (TETs), which is responsible for DNA demethylation, and DNA methyltransferases (DNMTs), which is responsible for DNA methylation. Second, m6A modification. m6A modification consists of three enzymes acting in combination with each other. Respectively, eraser: Fat mass and obesity associated (FTO) and AlkB homolog 5, RNA demethylase (ALKBH5). Writer: methyltransferase 3 (METTL3), methyltransferase 14 (METTL14) and so on. Reader: YTH N6-methyladenosine RNA binding protein F1/2/3 (YTHDF1/2/3), YTH N6-methyladenosine RNA binding protein C1/2/3 (YTHDC1/2/3) and insulin like growth factor 2 mRNA binding protein 1/2/3 (IGF2BP1/2/3). Third, histone modification, including histone acetylation, histone methylation, and histone ubiquitination. In addition, there are non-coding RNA modifications, including miRNAs, lncRNAs, and circRNA