RecA homology search is promoted by mechanical stress along the scanned duplex DNA.
A RecA-single-stranded DNA (RecA-ssDNA) filament searches a genome for sequence homology by rapidly binding and unbinding double-stranded DNA (dsDNA) until homology is found. We demonstrate that pulling on the opposite termini (3' and 5') of one of the two DNA strands in a dsDNA molecule stabilizes the normally unstable binding of that dsDNA to non-homologous RecA-ssDNA filaments, whereas pulling on the two 3', the two 5', or all four termini does not. We propose that the 'outgoing' strand in the dsDNA is extended by strong DNA-protein contacts, whereas the 'complementary' strand is extended by the tension on the base pairs that connect the 'complementary' strand to the 'outgoing' strand. The stress resulting from different levels of tension on its constitutive strands causes rapid dsDNA unbinding unless sufficient homology is present.
Department of Physics, Harvard University, Cambridge, MA 02138, USA.
Claudia
C
Danilowicz
Efraim
E
Feinstein
Alyson
A
Conover
Vincent W
VW
Coljee
Julea
J
Vlassakis
Yuen-Ling
YL
Chan
Douglas K
DK
Bishop
Mara
M
Prentiss
D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D011938:Rec A Recombinases / Q000378:metabolism*; D012399:Rotation; D012689:Sequence Homology, Nucleic Acid; D013314:Stress, Mechanical
D004277:DNA, Single-Stranded; D004247:DNA; D011938:Rec A Recombinases