Table 1.

Types of ncRNAs and their basic features.

Name	Abbreviation	Size	Location	Functions	Examples	Database	References
Ribosomal RNAs	rRNAs	6.9 kb	rDNA	Composition of ribosome	\*	NONCODE database	14
Transfer RNAs	tRNAs	<0.1 kb	tDNA	Amino acid transport	\*	NONCODE database	15
Small nucleolar RNAs	snoRNAs	60 to 300 bp	Intronic	Important function in the maturation of other ncRNAs/Association with development of some cancers	U50, S NORD	Starbase, PITA	26
Small nuclear RNAs	snRNAs	100 to 200 bp	\*	mRNAs splicing	U3, U6	miRanda	42
MicroRNAs	miRNAs	19 to 24 bp	Widespread loci	Targeting of mRNAs and many others/ Initiation of various disorders including many cancers	let-7	miRmap, miRSNP, MirBase	36
Transcribed ultraconserved regions	T-UCRs	>200 bp	Widespread loci	Regulations of miRNA and mRNA levels/Possible involvement in tumorigenesis	UCR106	ncRNA.org	112
PIWI-interacting RNAs	piRNAs	26 to 31 bp	Clusters, intragenic	Transposon repression or relationship with diseases has not been discovered	MIWI, MILI, MIWI2	piRNA BANK	23
Circular RNAs	circRNAs	~500 bp	Widespread loci	As endogenous competitive RNA/Association with many cancers and diseases	ciRs7, cANRIL	circRNAbase	25
Long non-coding RNAs	lncRNAs	>200 bp	Widespread loci	Scaffold DNA-chromatin complexes, X-chromosome inactivation/Involved in tumorigenesis and cancer metastasis	H19, XIST, HOTAIR, TSIX	lncRNA database, 3.0, LNCipedia	19

*No reference data.