期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：31
页码：12688-12693
DOI：10.1073/pnas.0811465106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Rad51 is a core component of the eukaryotic homologous recombination machinery and is responsible for key mechanistic steps during strand invasion. Higher order oligomers of Rad51 display a remarkable degree of structural variation, forming rings, compressed filaments, and elongated filaments. It is unclear whether Rad51 can transition directly between these different oligomeric structures without disassembling first into monomers. We have used single-molecule microscopy to investigate the behavior of human Rad51 assembled on double-stranded DNA. Our results show that human Rad51 can form elongated nucleoprotein filaments on DNA, but ATP hydrolysis causes a decrease in their length without concomitant dissociation of protein. Compressed Rad51 filaments can re-elongate when presented with either ATP or the non-hydrolyzable analog AMP-PNP, and these cycles of elongation and compression are reversible. A Rad51 mutant deficient in ATP hydrolysis is locked into an extended conformation that is incapable of transitioning to a compressed filament. Similarly, wild-type Rad51 bound to DNA in the presence of AMP-PNP was trapped in the elongated state. Proteins incapable of transitioning to the compressed state were also highly resistant to dissociation from the DNA. Taken together, our results indicate that nucleotide hydrolysis by human Rad51 triggers a reversible structural transition leading to filaments with reduced helical pitch.
关键词：DNA curtain ; homologous recombination ; single molecule imaging
