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.
Shinichi Machida  1 ,  Motoki Takaku  1 ,  Masae Ikura  2 ,  Jiying Sun  3 ,  Hidekazu Suzuki  3 ,  Wataru Kobayashi  4 ,  Aiko Kinomura  3 ,  Akihisa Osakabe  4 ,  Hiroaki Tachiwana  4 ,  Yasunori Horikoshi  3 ,  Atsuhiko Fukuto  3 ,  Ryo Matsuda  2 ,  Kiyoe Ura  5 ,  Satoshi Tashiro  3 ,  Tsuyoshi Ikura  2 ,  Hitoshi Kurumizaka  4
Affiliations
  • 1. 1] Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan [2].
  • 2. Department of Mutagenesis, Division of Chromatin Regulatory Network, Radiation Biology Center, Kyoto University, Yoshidakonoe, Sakyo-ku, Kyoto 606-8501, Japan.
  • 3. Department of Cellular Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
  • 4. Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
  • 5. Division of Gene Therapy Science, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
PMID: 24798879 DOI: 10.1038/srep04863
Abstract

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.