title: Hop2/Mnd1 acts on two critical steps in Dmc1-promoted homologous pairing.
abstract: Meiotic recombination between homologous chromosomes ensures their proper segregation at the first division of meiosis and is the main force shaping genetic variation of genomes. The HOP2 and MND1 genes are essential for this recombination: Their disruption results in severe defects in homologous chromosome synapsis and an early-stage failure in meiotic recombination. The mouse Hop2 and Mnd1 proteins form a stable heterodimer (Hop2/Mnd1) that greatly enhances Dmc1-mediated strand invasion. In order to elucidate the mechanism by which Hop2/Mnd1 stimulates Dmc1, we identify several intermediate steps in the homologous pairing reaction promoted by Dmc1. We show that Hop2/Mnd1 greatly stimulates Dmc1 to promote synaptic complex formation on long duplex DNAs, a step previously revealed only for bacterial homologous recombinases. This synaptic alignment is a consequence of the ability of Hop2/Mnd1 to (1) stabilize Dmc1-single-stranded DNA (ssDNA) nucleoprotein complexes, and (2) facilitate the conjoining of DNA molecules through the capture of double-stranded DNA by the Dmc1-ssDNA nucleoprotein filament. To our knowledge, Hop2/Mnd1 is the first homologous recombinase accessory protein that acts on these two separate and critical steps in mammalian meiotic recombination.
authors.affiliation: Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Roberto J
authors.initials: RJ
authors.lastname: Pezza
authors.forename: Oleg N
authors.initials: ON
authors.lastname: Voloshin
authors.forename: Filip
authors.initials: F
authors.lastname: Vanevski
authors.forename: R Daniel
authors.initials: RD
authors.lastname: Camerini-Otero
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D023902:Chromosome Pairing / Q000502:physiology*; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008954:Models, Biological; D046912:Multiprotein Complexes; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; C501202:Hop2 protein, mouse; C501203:Mnd1 protein, mouse; D046912:Multiprotein Complexes; D011994:Recombinant Proteins; C074556:DMC1 protein, human