title: Saccharomyces cerevisiae Hop1 protein zinc finger motif binds to the Holliday junction and distorts the DNA structure: implications for holliday junction migration.
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 Cys371 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, KMnO4 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 Zn2+, 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.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Tripathi
authors.forename: Debnath
authors.initials: D
authors.lastname: Pal
authors.forename: K
authors.initials: K
authors.lastname: Muniyappa
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D004265:DNA Helicases / Q000378:metabolism; D045566:DNA, Cruciform / Q000378:metabolism*; D004271:DNA, Fungal / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D017510:Protein Folding; D053484:RecQ Helicases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D016335:Zinc Fingers / Q000502:physiology*
chemical_list: D045566:DNA, Cruciform; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C086672:HOP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; D004265:DNA Helicases; D053484:RecQ Helicases