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The widespread impact of mammalian MicroRNAs on mRNA repression and evolution.

Thousands of mammalian messenger RNAs are under selective pressure to maintain 7-nucleotide sites matching microRNAs (miRNAs). We found that these conserved targets are often highly expressed at developmental stages before miRNA expression and that their levels tend to fall as the miRNA that targets them begins to accumulate. Nonconserved sites, which outnumber the conserved sites 10 to 1, also mediate repression. As a consequence, genes preferentially expressed at the same time and place as a miRNA have evolved to selectively avoid sites matching the miRNA. This phenomenon of selective avoidance extends to thousands of genes and enables spatial and temporal specificities of miRNAs to be revealed by finding tissues and developmental stages in which messages with corresponding sites are expressed at lower levels.

Pubmed ID: 16308420


  • Farh KK
  • Grimson A
  • Jan C
  • Lewis BP
  • Johnston WK
  • Lim LP
  • Burge CB
  • Bartel DP


Science (New York, N.Y.)

Publication Data

December 16, 2005

Associated Grants


Mesh Terms

  • Animals
  • Base Sequence
  • Cell Differentiation
  • Conserved Sequence
  • Evolution, Molecular
  • Gene Expression Profiling
  • Gene Expression Regulation
  • Humans
  • Mammals
  • Mice
  • MicroRNAs
  • Molecular Sequence Data
  • Muscle Fibers, Skeletal
  • Organ Specificity
  • RNA Stability
  • RNA, Messenger
  • Rats
  • Species Specificity
  • Untranslated Regions
  • Zebrafish