from Jeffrey E. Squires and Thomas Preiss writing in Epigenetics: A Reference Manual:
A wealth of nucleobase and ribose modifications have been identified in multiple types of RNA including tRNAs, rRNAs, mRNAs, and small regulatory RNAs. Among them, 5-methylcytosine (m5C) has been detected in rRNAs, tRNAs, and early reports have indicated its presence in mRNAs. Well established as an epigenetic mark in DNA, the prevalence and function of m5C in RNA is either incompletely explored (tRNA, rRNA) or virtually unknown (mRNA, other noncoding RNA). Two eukaryotic m5C RNA methyltransferases have been identified; however, their substrate specificity and biological roles are incompletely understood. With recent advances in bisulfite sequencing of RNA, comprehensive analyses to determine the occurrence and functions of m5C in the transcriptome now appear feasible. In this chapter, we summarise the current knowledge in this field, focussing primarily on eukaryotic transcriptomes.
Further reading: Epigenetics: A Reference Manual