Ca2+ Activates Human Homologous Recombination Protein Rad51 by Modulating Its ATPase Activity

• Published in: Proceedings of the National Academy of Sciences - PNAS 2004-07, Vol.101 (27), p.9988-9993
• Main Authors: Bugreev, Dmitry V., Mazin, Alexander V.
• Format: Article
• Language: English
• Subjects: Adenosine Diphosphate - metabolism; Adenosine triphosphatases; Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - metabolism; Biochemistry; Biological Sciences; Calcium - pharmacology; DNA; DNA - metabolism; DNA repair; DNA-Binding Proteins - metabolism; Fluorescence; Gels; Gene expression regulation; Hydrolysis; Magnesium - pharmacology; Molecules; Nucleoproteins; Proteins; Rad51 Recombinase; Sodium Chloride - pharmacology; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0402105101

Human Rad51 (hRad51) protein plays a key role in homologous recombination and DNA repair. hRad51 protein forms a helical filament on single-stranded DNA (ssDNA), which performs the basic steps of homologous recombination: a search for homologous double-stranded DNA (dsDNA) and DNA strand exchange. hRad51 protein possesses DNA-dependent ATPase activity; however, the role of this activity has not been understood. Our current results show that Ca2+ greatly stimulates DNA strand exchange activity of hRad51 protein. We found that Ca2+ exerts its stimulatory effect by modulating the ATPase activity of hRad51 protein. Our data demonstrate that, in the presence of Mg2+, the hRad51-ATP-ssDNA filament is quickly converted to an inactive hRad51-ADP-ssDNA form, due to relatively rapid ATP hydrolysis and slow dissociation of ADP. Ca2+ maintains the active hRad51-ATP-ssDNA filament by reducing the ATP hydrolysis rate. These findings demonstrate a crucial role of the ATPase activity in regulation of DNA strand exchange activity of hRad51 protein. This mechanism of Rad51 protein regulation by modulating its ATPase activity is evolutionarily recent; we found no such mechanism for yeast Rad51 (yRad51) protein.