Table 2.

Summary of RNA m⁵C regulators

Regulator		Molecular structure	Catalytic substrate	Cellular distribution	Cellular processes involved
Writer	NSUN2	A SAM binding site and a catalytic domain, which contains two cysteine residues	tRNA at position C34, 40, 48–50, mRNA (near the start codons and stop codons in coding sequence, also in untranslated region), rRNA, viral RNA, vault RNA	G1 phase: nucleolus, S phase: between nucleolus and nucleoplasm, G2 phase: cytoplasm, M phase: centrioles	Root development of plants, mitochondrial oxidative phosphorylation, protein synthesis, cell cycle progression, HIV replication, Epstein-Barr virus degradation, epidermal differentiation and tumorigenesis
	NUSN1		25 s rRNA at position C2870 in domain V	Predominantly nucleolus and weaker cytoplasmic staining	Tumor aggressiveness, cell cycle progression, chromatins organization and HIV-1 latency
	NSUN4		12S rRNA at position C911	Mitochondria	Tumorigenesis
	NUUN5		25 s rRNA at position C2278 in domain IV	Nucleolus	Cell senescence and stress response
	NSUN3		mt-tRNAMet at wobble base C34	Mitochondria	Mitochondrial oxidative phosphorylation, embryonic stem cell differentiation
	NSUN6		tRNACys and tRNAThr at position C72	Golgi apparatus and pericentriolar matrix	tRNA biogenesis
	DNMT2	A SAM binding site and a catalytic domain, which contains one cysteine residue	tRNAAsp-GTC, tRNAGly-GCC and tRNAVal-AAC at position C38, mRNA	Cytoplasm	Tumorigenesis, protein synthesis, cell differentiation, malarial parasite pathogenicity and HIV-1 RNA survival
Eraser	TET1	–	Coding and non-coding RNAs	Nucleus	5-methylcytidine oxidation
	TET2	–		Nucleus
	TET3	–		Nucleus and cytoplasm
Reader	ALYREF	–	mRNA and retroviral RNA	Nucleus	mRNA nuclear-cytoplasmic shuttling, viral RNA export and replication
	YBX1	A cold-shock domain	mRNA	Cytoplasm	mRNA stabilization, embryogenesis, tumorigenesis