Small noncoding RNAs, such as the ~21 nucleotide (nt) let-7 RNA, regulate the developmental timing of the nematode Caenorhabditis elegans. These RNAs are highly conserved in many bilaterally symmetrical organisms, including humans. The similarity in size between the let-7 RNA and those generated during RNA interference (RNAi), in which RNA blocks gene expression, has led to the suggestion that the two may be linked. Hutvágner et al. (see the Perspective by Ambros) now show that the enzyme Dicer, which is implicated as the ribonuclease involved in the generation of the small 21- to 23-nt interfering RNAs in RNAi, is also responsible for cleaving the putative ~70-nt let-7 precursor to generate the let-7 RNA.
G. Hutvágner, J. McLachlan, A. E. Pasquinelli, É. Bálint, T. Tuschl, P. D. Zamore, A cellular function for the RNA-interference enzyme dicer in the maturation of the let-7 small temporal RNA. Science 293, 834-838 (2001). [Abstract] [Full Text]
V. Ambros, Dicing up RNAs. Science 293, 811-813 (2001). [Full Text]