Nap1 stimulates homologous recombination by RAD51 and RAD54 in higher-ordered chromatin containing histone H1

Sci Rep. 2014 May 6;4:4863. doi: 10.1038/srep04863.


Homologous recombination plays essential roles in mitotic DNA double strand break (DSB) repair and meiotic genetic recombination. In eukaryotes, RAD51 promotes the central homologous-pairing step during homologous recombination, but is not sufficient to overcome the reaction barrier imposed by nucleosomes. RAD54, a member of the ATP-dependent nucleosome remodeling factor family, is required to promote the RAD51-mediated homologous pairing in nucleosomal DNA. In higher eukaryotes, most nucleosomes form higher-ordered chromatin containing the linker histone H1. However, the mechanism by which RAD51/RAD54-mediated homologous pairing occurs in higher-ordered chromatin has not been elucidated. In this study, we found that a histone chaperone, Nap1, accumulates on DSB sites in human cells, and DSB repair is substantially decreased in Nap1-knockdown cells. We determined that Nap1 binds to RAD54, enhances the RAD54-mediated nucleosome remodeling by evicting histone H1, and eventually stimulates the RAD51-mediated homologous pairing in higher-ordered chromatin containing histone H1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Cell Line
  • Chromatin / genetics
  • Chromatin / metabolism*
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • DNA Repair / genetics
  • DNA Repair Enzymes / genetics
  • DNA Repair Enzymes / metabolism
  • DNA-Binding Proteins
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Histones / genetics
  • Histones / metabolism*
  • Homologous Recombination / genetics*
  • Humans
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Nucleosomes / genetics
  • Nucleosomes / metabolism
  • Proteins / metabolism*
  • Rad51 Recombinase / genetics
  • Rad51 Recombinase / metabolism*
  • tRNA Methyltransferases


  • Chromatin
  • DNA-Binding Proteins
  • Histones
  • Nuclear Proteins
  • Nucleosomes
  • Proteins
  • TRMO protein, human
  • tRNA Methyltransferases
  • Rad51 Recombinase
  • Adenosine Triphosphatases
  • DNA Helicases
  • RAD54L protein, human
  • DNA Repair Enzymes