Table 1. Classification of functional ncRNAs. Transcriptional gene silencing functions of short (grey background) and long ncRNAs by chromatin interaction.

ncRNA class	Chromatin interaction
MicroRNA (miRNA)	Yes 114
Small interfering RNA (siRNA)	Yes 115
Piwi-interacting RNA (piRNA)	Yes 116
Small nuclearRNA (snRNA)	Yes 92
Small nucleolarRNA (snoRNA)	Yes 117
Natural antisense transcript (NAT)	Yes80
Large intergenic ncRNA (lincRNA)	Yes35
Promoter associated RNA (paRNA)	Yes118
Circular RNA (circRNA)	Yes78
Enhancer RNA (eRNA)	Yes119
Pseudogene RNA (trans-NAT)	Yes120,121
Transcribed ultraconserved regions (T-UCRs)	Yes122
Short-lived RNA transcripts (SLiTs)	Yes32
Telomeric repeat-containing RNA (TERRA)	Yes123
Transfer RNA (tRNA)	Not reported
Ribosomal RNA (rRNA)	Not reported