title: Homologous pairing activities of two rice RAD51 proteins, RAD51A1 and RAD51A2.
abstract: In higher eukaryotes, RAD51 functions as an essential protein in homologous recombination and recombinational repair of DNA double strand breaks. During these processes, RAD51 catalyzes homologous pairing between single-stranded DNA and double-stranded DNA. Japonica cultivars of rice (Oryza sativa) encode two RAD51 proteins, RAD51A1 and RAD51A2, whereas only one RAD51 exists in yeast and mammals. However, the functional differences between RAD51A1 and RAD51A2 have not been elucidated, because their biochemical properties have not been characterized. In the present study, we purified RAD51A1 and RAD51A2, and found that RAD51A2 robustly promotes homologous pairing in vitro. RAD51A1 also possesses homologous-pairing activity, but it is only about 10% of the RAD51A2 activity. Both RAD51A1 and RAD51A2 bind to ssDNA and dsDNA, and their DNA binding strictly requires ATP, which modulates the polymer formation activities of RAD51A1 and RAD51A2. These findings suggest that although both RAD51A1 and RAD51A2 have the potential to catalyze homologous pairing, RAD51A2 may be the major recombinase in rice.
authors.affiliation: Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Shinjuku, Tokyo, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Morozumi
authors.forename: Ryohei
authors.initials: R
authors.lastname: Ino
authors.forename: Shukuko
authors.initials: S
authors.lastname: Ikawa
authors.forename: Naozumi
authors.initials: N
authors.lastname: Mimida
authors.forename: Takeshi
authors.initials: T
authors.lastname: Shimizu
authors.forename: Seiichi
authors.initials: S
authors.lastname: Toki
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ichikawa
authors.forename: Takehiko
authors.initials: T
authors.lastname: Shibata
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kurumizaka
mesh_terms: D053903:DNA Breaks, Double-Stranded; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D051135:Rad51 Recombinase