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Updated: Jun 21, 2026
12:02
Molecular Evolution of the Tre Recombinase
Published on: May 29, 2008
A molecular throttle: the recombination hotspot chi controls DNA translocation by the RecBCD helicase
Maria Spies1, Piero R Bianco, Mark S Dillingham
1Section of Microbiology, Center for Genetics and Development, University of California, Davis 9561, USA.
Cell
|September 19, 2003
Summary
The RecBCD enzyme, crucial for DNA repair, pauses at the chi sequence. This interaction slows its DNA translocation speed by half, suggesting a motor subunit uncoupling.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- RecBCD enzyme is a key helicase/nuclease initiating homologous recombination at DNA breaks.
- The DNA sequence chi regulates RecBCD enzyme's nuclease activity and RecA loading.
- Chi recognition influences RecBCD enzyme's interaction with DNA.
Purpose of the Study:
- To investigate the effect of the chi sequence on RecBCD enzyme translocation dynamics.
- To elucidate the mechanism by which chi influences RecBCD enzyme activity.
Main Methods:
- Single-molecule DNA translocation assays were used to observe individual RecBCD enzyme movements.
- Real-time observation of RecBCD enzyme translocation along DNA molecules.
Main Results:
- RecBCD enzyme was observed to pause precisely at the chi DNA sequence.
- Following the pause at chi, RecBCD enzyme's translocation rate decreased by approximately 50% of its initial speed.
- This suggests a change in the enzyme's motor function upon chi interaction.
Conclusions:
- The chi sequence modulates RecBCD enzyme translocation, causing a significant pause and subsequent rate reduction.
- This modulation is proposed to result from the uncoupling of a motor subunit, likely RecD, from the holoenzyme.
- This mechanism provides new insights into the regulation of DNA repair and recombination initiation.
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