Table 1 Functional classification of non-protein-coding RNA transcripts

Housekeeping RNAs

tRNA

Translation of genetic information

rRNA

Ribosome components; catalysis of peptide bond formation

snRNA

Pre-mRNA splicing; spliceosome components

snoRNA

RNA modification, including 2'-O-methylation and pseudouridylation

RNase P RNA

Maturation of 5' ends of pre-tRNA

Telomerase RNA

Telomeric DNA synthesis; component of telomerase

4.5S RNA

Protein export in bacteria

7SL RNA

Protein export in eukaryotes

tmRNA

Trans-translation

Y RNA

Ro RNP components; function unknown

RNase MRP

Mitochondrial RNA processing

Regulatory RNAs

Transcriptional regulators

roX RNAs and Xist/Tsix

Chromatin remodeling associated with X-chromosome inactivation and dosage compensation in eukaryotes

H19, IPW and LIT1

Regulation of expression of imprinted genes

   Post-transcriptional regulators

DsrA, micF, lin-4, let-7, microRNAs, HFE and LjPLP-IV

Repression or stimulation of translation of regulated mRNAs in eukaryotic and prokaryotic cells via antisense RNA:RNA interactions

   Modulators of protein function

6S RNA, OxyS and SRA

Modulation of protein activity via RNA-protein interactions

Regulators of RNA and protein distribution

Xlsirt and hsr-ω

Effects on localization of mRNA or pre-mRNA depending on specific subcellular location of non-coding RNA