Table 1.

Classification of non-coding RNAs.

Housekeeping ncRNA	Symbol	Function
	rRNA (ribosomial)	mRNA translation
	tRNA (transfer)	mRNA translation
	snoRNA (small nucleolar RNA)	RNA modification, rRNA procesing
Regulatory ncRNA	Symbol	Function
Short ncRNA (<200 nt)	piRNA (PIWI-interacting RNA)	DNA methylation, transposition repression
	miRNA (microRNA)	Transcriptional regulation
	siRNA (short interfering RNA)	RNA interference
lncRNA (>200 nt)	lincRNA (long intergenic RNA)	Epigenetic regulation of transcription
	eRNA (enhancer-like ncRNA)	Transcriptional gene activation
	T-UCR (transcribed ultraconserved regions)	Regulation of miRNA and mRNA levels
	NAT (natural antisense transcripts)	mRNA stability
	PALR (promoter-associated long RNA)	Chromatin changes