An abundant class of tiny RNAs with probable regulatory roles in Caenorhabditis elegans

Science. 2001 Oct 26;294(5543):858-62. doi: 10.1126/science.1065062.


Two small temporal RNAs (stRNAs), lin-4 and let-7, control developmental timing in Caenorhabditis elegans. We find that these two regulatory RNAs are members of a large class of 21- to 24-nucleotide noncoding RNAs, called microRNAs (miRNAs). We report on 55 previously unknown miRNAs in C. elegans. The miRNAs have diverse expression patterns during development: a let-7 paralog is temporally coexpressed with let-7; miRNAs encoded in a single genomic cluster are coexpressed during embryogenesis; and still other miRNAs are expressed constitutively throughout development. Potential orthologs of several of these miRNA genes were identified in Drosophila and human genomes. The abundance of these tiny RNAs, their expression patterns, and their evolutionary conservation imply that, as a class, miRNAs have broad regulatory functions in animals.

MeSH terms

  • Animals
  • Base Sequence
  • Blotting, Northern
  • Caenorhabditis elegans / genetics*
  • Cloning, Molecular
  • Conserved Sequence
  • Endoribonucleases / metabolism
  • Gene Expression Regulation*
  • Gene Expression Regulation, Developmental
  • Genes, Helminth
  • Genome
  • Humans
  • Molecular Sequence Data
  • Multigene Family
  • Nucleic Acid Conformation
  • RNA Precursors / genetics
  • RNA Precursors / metabolism
  • RNA, Helminth / chemistry*
  • RNA, Helminth / genetics*
  • RNA, Helminth / physiology
  • RNA, Untranslated / chemistry
  • RNA, Untranslated / genetics*
  • RNA, Untranslated / physiology
  • Ribonuclease III
  • Transcription, Genetic


  • RNA Precursors
  • RNA, Helminth
  • RNA, Untranslated
  • Endoribonucleases
  • Ribonuclease III