So far, over 170 types of RNA modifications have been identified, and these modifications are widely distributed in non-coding RNAs. With the advancement of detection techniques, various chemical modifications have been detected on mRNA in higher eukaryotes, giving rise to the emerging field of epitranscriptomics. This has reshaped our understanding of post-transcriptional regulation and propelled the development of RNA biology.

N6-methyladenosine (m6A) is the most abundant chemical modification on eukaryotic mRNA and is currently the most extensively studied modification. In the past decade, regulatory proteins (methyltransferases, binding proteins, and demethylases) for this modification have been discovered, and various whole transcriptome sequencing techniques have been developed. These advancements have facilitated the analysis of the biological functions and regulatory mechanisms of m6A modification.

Apart from m6A, other chemical modifications exist on mRNA, including pseudouridine (Ψ), N1-methyladenosine (m1A), 5-methylcytosine (m5C), N6,2′-O-dimethyladenosine (m6Am), inosine, N4-acetylcytidine (ac4C), 2′-O-methylguanosine (Nm), and internal N7-methylguanosine (m7G). Similar to m6A modification, the advancement of sequencing methods and the identification of regulatory effect proteins have driven research into the synthesis, distribution characteristics, molecular functions, and regulatory mechanisms of modifications beyond m6A. Additionally, extensive research indicates that other modifications to mRNA play crucial regulatory roles in important physiological processes and human diseases.

Currently, most reviews about epitranscriptomic modifications focus on m6A modifications, making a comprehensive introduction to other types of chemical modifications on mRNA particularly necessary. This review primarily discusses the regulatory mechanisms and biological functions of modifications other than m6A on mRNA. It provides detailed insights into known effect proteins, detection techniques, distribution characteristics, and their functions in mRNA metabolism under physiological and pathological conditions. The review also covers future research techniques and potential applications for modifications beyond m6A on mRNA.