Table 1. Small RNAs Involved in Gene Silencing.
class | size (nt) | function | origin | species |
---|---|---|---|---|
microRNAs | 21–25 | translation repression and mRNA destabilization | miR-coding genes, introns (mirtrons) | C. elegans, D. melanogaster, A. thaliana, O. sativa, mammals |
endo-siRNAs | 21–25 | transposon silencing and mRNA degradation | transposons, pseudogenes | D. melanogaster, C. elegans, mammals |
siRNAs | 21–25 | mRNA degradation and transposon silencing | intergenic regions, exons and introns | C. elegans, D. melanogaster, S. pombe, A. thaliana, O. sativa |
piRNAs | 24–31a | transposon silencing, spermatogenesis | transposons and other repeat sequences | C. elegans, D. melanogaster, Danio rerio, mammals |
piRNAs in C. elegans are ∼21 nt in length.