Table 1.

Types of ncRNAs and their known functions.

ncRNA Species	General Functions and Properties
miRNA	Fine regulators of expression
	Inhibition of gene transcription
lncRNA	Interference in polymerase activity
	Antisense RNA sequence matching
	Inhibition of histone acetyltransferase activity and repression of transcription
	Recruitment of transcriptional regulators
	Upregulate translation without altering mRNA levels
	Chromatin remodeling
	Enhancer
	Histone modifications and DNA methylation
piRNA	Block transposable elements
	Regulators of transcription acting primarily on transposable element sequences
	Protection against external nucleic acids
circRNA	Monitor the production of linear transcripts of RNA and microRNAs
	Sponge-like regulatory system decreasing miRNA concentration in the cytoplasm
	Can bind RNA-binding proteins
tRNA	Protein synthesis.
	Post- or pre-transcriptional regulators of gene expression
rRNA	Ribosomal subunits (5S, 16S, 23S, 5.8S, 18S and 28S)
	Protein synthesis