Glimpses of a Tiny RNA World

Naturally tiny regulatory RNAs of about 22 nucleotides were first identified from Caenorhabditis elegans genetics. Artificially induced RNAs of this size are also an intermediate in RNA interference, and both such RNAs use a common biochemical processing pathway. Now three groups have shown that there is an entire world of tiny RNAs that had almost escaped detection until now. These tiny RNAs are likely to regulate the translation of other mRNAs during development and, like the intermediates in RNAi, may be subject to amplification and systemic spread.