Abstract
The Escherichia coli RuvA and RuvB proteins promote the branch migration of Holliday junctions during the late stages of homologous recombination and DNA repair (reviewed in [1]). Biochemical and structural studies of the RuvAB-Holliday junction complex have shown that RuvA binds directly to the Holliday junction [2-6] and acts as a specificity factor that promotes the targeting of RuvB [7,8], a hexameric ring protein that drives branch migration [9-11]. Electron microscopic visualisation of the RuvAB complex revealed that RuvA is flanked by two RuvB hexamers, which bind DNA arms that lie diametrically opposed across the junction [8]. ATP-dependent branch migration occurs as duplex DNA is pumped out through the centre of each ring. Because RuvB possesses well-conserved helicase motifs and RuvAB exhibits a 5'-3' DNA helicase activity in vitro [12], the mechanism of branch migration is thought to involve DNA opening within the RuvB ring, which provides a single strand for the unidirectional translocation of the protein along DNA. We have investigated whether the RuvB ring can translocate along duplex DNA containing a site-directed interstrand psoralen crosslink. Surprisingly, we found that the crosslink failed to inhibit branch migration. We interpret these data as evidence against a base-by-base tracking model and suggest that extensive DNA opening within the RuvB ring is not required for DNA translocation by RuvB.
Original language | English (US) |
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Pages (from-to) | 103-106 |
Number of pages | 4 |
Journal | Current Biology |
Volume | 10 |
Issue number | 2 |
DOIs | |
State | Published - Jan 1 2000 |
Externally published | Yes |
ASJC Scopus subject areas
- General Neuroscience
- General Biochemistry, Genetics and Molecular Biology
- General Agricultural and Biological Sciences