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The recombination hotspot chi is a regulatory sequence that acts by attenuating the nuclease activity of the E. coli RecBCD enzyme.

Authors
Type
Published Article
Journal
Cell
0092-8674
Publisher
Elsevier
Volume
73
Issue
1
Pages
87–96
Source
Kowalczykowski Lab

Abstract

The RecBCD enzyme is a multifunctional enzyme that is essential for homologous recombination in E. coli. In vitro, the RecBCD enzyme degrades linear double-stranded DNA nonspecifically during the process of unwinding the double-stranded DNA. Here we demonstrate that this DNA degradation is asymmetric, with the strand that is 3 terminal at the entry site of RecBCD enzyme being degraded much more vigorously than the 5 terminal strand. Furthermore, interaction with the recombination hotspot chi causes an attenuation of the nuclease activity but not of the helicase activity and is accompanied by a pause of RecBCD enzyme at the chi site. These results demonstrate that chi is a unique regulatory element that acts by controlling the degradative function of RecBCD enzyme and, thereby, enhancing its recombination function.

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