Promoter-bound trinucleotide repeat mRNA drives epigenetic silencing in fragile X syndrome

Science. 2014 Feb 28;343(6174):1002-5. doi: 10.1126/science.1245831.

Abstract

Epigenetic gene silencing is seen in several repeat-expansion diseases. In fragile X syndrome, the most common genetic form of mental retardation, a CGG trinucleotide-repeat expansion adjacent to the fragile X mental retardation 1 (FMR1) gene promoter results in its epigenetic silencing. Here, we show that FMR1 silencing is mediated by the FMR1 mRNA. The FMR1 mRNA contains the transcribed CGG-repeat tract as part of the 5' untranslated region, which hybridizes to the complementary CGG-repeat portion of the FMR1 gene to form an RNA·DNA duplex. Disrupting the interaction of the mRNA with the CGG-repeat portion of the FMR1 gene prevents promoter silencing. Thus, our data link trinucleotide-repeat expansion to a form of RNA-directed gene silencing mediated by direct interactions of the trinucleotide-repeat RNA and DNA.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • DNA Methylation
  • Embryonic Stem Cells / metabolism
  • Fragile X Mental Retardation Protein / genetics*
  • Fragile X Syndrome / genetics*
  • Gene Silencing*
  • Humans
  • Mice
  • Mice, Inbred NOD
  • Mice, SCID
  • Neurons / metabolism
  • Nuclear Proteins / genetics
  • Promoter Regions, Genetic / genetics
  • RNA, Messenger / genetics*
  • RNA, Small Interfering / genetics
  • Trinucleotide Repeats / genetics*

Substances

  • AFF2 protein, human
  • FMR1 protein, human
  • Nuclear Proteins
  • RNA, Messenger
  • RNA, Small Interfering
  • Fragile X Mental Retardation Protein