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Mol Cell. 2003 Sep;12(3):747-59.

The endogenous Mus81-Eme1 complex resolves Holliday junctions by a nick and counternick mechanism.

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1
Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.

Abstract

Functional studies strongly suggest that the Mus81-Eme1 complex resolves Holliday junctions (HJs) in fission yeast, but in vitro it preferentially cleaves flexible three-way branched structures that model replication forks or 3' flaps. Here we report that a nicked HJ is the preferred substrate of endogenous and recombinant Mus81-Eme1. Cleavage occurs specifically on the strand that opposes the nick, resulting in resolution of the structure into linear duplex products. Resolving cuts made by the endogenous Mus81-Eme1 complex on an intact HJ are quasi-simultaneous, indicating that Mus81-Eme1 resolves HJs by a nick and counternick mechanism, with a large rate enhancement of the second cut arising from the flexible nature of the nicked HJ intermediate. Recombinant Mus81-Eme1 is ineffective at making the first cut. We also report that HJs accumulate in a DNA polymerase alpha mutant that lacks Mus81, providing further evidence that the Mus81-Eme1 complex targets HJs in vivo.

PMID:
14527419
DOI:
10.1016/s1097-2765(03)00342-3
[Indexed for MEDLINE]
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