Saccharomyces cerevisiae Hop1 Protein Zinc Finger Motif Binds to the Holliday Junction and Distorts the DNA Structure: Implications for Holliday Junction

Tripathi, Pankaj and Pal, Debnath and Muniyappa, K (2007) Saccharomyces cerevisiae Hop1 Protein Zinc Finger Motif Binds to the Holliday Junction and Distorts the DNA Structure: Implications for Holliday Junction. In: Biochemistry, 46 (44). pp. 12530-12542.

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Abstract

Saccharomyces cereVisiae HOP1, which encodes a component of synaptonemal complex, plays an important role in crossing over between homologues. Hop1p contains a zinc finger motif, and substitution of a conserved $Cys^{371}$ by Ser rendered the hop1 mutant allele defective in sporulation and meiosis. However, the molecular mechanism underlying the function of Hop1 zinc finger motif (ZnF) remains obscure. Here we show that wild-type Hop1 ZnF binds significantly better to the Holliday junction compared with other recombination intermediates. Consequently, the salt titration midpoint for dissociation of the Holliday junction-ZnF complex was higher than the complexes containing flush-ended linear or tailed duplex DNA. Although DNase I footprinting showed that Hop1 ZnF binds to each of the four arms of the junction, $KMnO_4$ probing and 2-aminopurine fluorescence emission data disclosed that it distorts the DNA structure along a pair of symmetrical arms. Molecular modeling studies show that Hop1 ZnF forms a unique zinc binding fold, reminiscent of the basic helix-loop-helix motif. In the presence of $Zn^{2+}$, docking studies show that $\alpha$ helix 1, which is replete with basic amino acid residues, makes stabilizing contacts with the sugar-phosphate backbone. Structural comparison revealed a striking similarity between RecG wedge domain and Hop1 ZnF motif. We propose that Hop1 ZnF motif plays a key role in the physical monitoring of recombination intermediates and branch migration of the Holliday junction.

Item Type:	Journal Article
Publication:	Biochemistry
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	18 Dec 2008 07:40
Last Modified:	19 Sep 2010 04:52
URI:	http://eprints.iisc.ac.in/id/eprint/16495

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