Inactivation of the SR protein splicing factor ASF/SF2 results in genomic instability

Cell. 2005 Aug 12;122(3):365-78. doi: 10.1016/j.cell.2005.06.008.


SR proteins constitute a family of pre-mRNA splicing factors now thought to play several roles in mRNA metabolism in metazoan cells. Here we provide evidence that a prototypical SR protein, ASF/SF2, is unexpectedly required for maintenance of genomic stability. We first show that in vivo depletion of ASF/SF2 results in a hypermutation phenotype likely due to DNA rearrangements, reflected in the rapid appearance of DNA double-strand breaks and high-molecular-weight DNA fragments. Analysis of DNA from ASF/SF2-depleted cells revealed that the nontemplate strand of a transcribed gene was single stranded due to formation of an RNA:DNA hybrid, R loop structure. Stable overexpression of RNase H suppressed the DNA-fragmentation and hypermutation phenotypes. Indicative of a direct role, ASF/SF2 prevented R loop formation in a reconstituted in vitro transcription reaction. Our results support a model by which recruitment of ASF/SF2 to nascent transcripts by RNA polymerase II prevents formation of mutagenic R loop structures.

Publication types

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

MeSH terms

  • Actins / genetics
  • Alternative Splicing / genetics
  • Alternative Splicing / physiology
  • Animals
  • Cell Death / physiology
  • Cell Line
  • Genomic Instability*
  • Humans
  • Mutation
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism*
  • Phenotype
  • RNA Polymerase II / genetics
  • RNA Splicing / genetics
  • RNA Splicing / physiology
  • RNA-Binding Proteins
  • Ribonuclease H / genetics
  • Ribonuclease H / metabolism
  • Serine-Arginine Splicing Factors
  • Time Factors


  • Actins
  • Nuclear Proteins
  • RNA-Binding Proteins
  • Serine-Arginine Splicing Factors
  • RNA Polymerase II
  • Ribonuclease H