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. Author manuscript; available in PMC: 2019 Jul 1.
Published in final edited form as: Wiley Interdiscip Rev RNA. 2018 May 3;9(4):e1477. doi: 10.1002/wrna.1477

Table 1.

Classes of mammalian RNAs and their lengths, localization, and function.

RNA Class Length Subcellular Localization Function
Micro RNA (miRNA) 20-25 nt Cytoplasm Decay of target mRNA
Piwi-interacting RNA
(piRNA) 		26-31 nt Nucleus Directing chromatin modification to repress transcription
Transfer RNA
(tRNA) 		70-90 nt Cytoplasm Decoding mRNA sequence during translation
Small nucleolar RNA
(snoRNA) 		60-200 nt Nucleus Guide for pre-ribosomal RNA processing and modification
Small nuclear RNA
(snRNA) 		100-300 nt Nucleus Splicing
Long non-coding RNA
(lncRNA) 		>200 nt Nucleus and Cytoplasm Transcriptional, epigenetic, and translational control
Ribosomal RNA
(rRNA) 		2-5 kb Cytoplasm Major component of translation machinery
Messenger RNA
(mRNA) 		2-5 kb Nucleus and Cytoplasm Contains regions that both regulate and code for protein synthesis

Abbreviations: nt, nucleotide; kb, kilobase.