Chemical Approaches for Structure and Function of RNA in Postgenomic Era

Table 5

Examples of modification. All RNA species including high- and low-molecular-weight RNAs have their own signature sequences and modifications.

RNA	Sequence and signature modification
hnRNAs; (Exons + Introns)	m^7G cap, m^6A, Poly-A,; splicing codes
mRNAs; (mainly exons)	m^7G cap, m^6A, Poly-A; Editing (C→U & A→I)
tRNAs	TΨC, CCA,; Many hypermodified bases
45S pre-rRNA	Repeated U sequences at 5′ end spacers
18S rRNA	m26A, hypermodified m^1acp^3Ψ
28S rRNA	NmNmNmN, NmNmN
snRNAs, snoRNAs	m32,2,7G cap, mγG cap; Types I, II, and III caps by ribose; methylations
mRNA; (Trypanosome)	m^7Gpppm26,6AmpAmpCmpm^3UmpAp; Insertion of repeated U sequence; Deletion of U sequence