title: Presynapsis and synapsis of DNA promoted by the STP alpha and single-stranded DNA-binding proteins from Saccharomyces cerevisiae.
abstract: We previously purified an activity from meiotic cell extracts of Saccharomyces cerevisiae that promotes the transfer of a strand from a duplex linear DNA molecule to complementary circular single-stranded DNA, naming it Strand Transfer Protein alpha (STP alpha) (Sugino, A., Nitiss, J., and Resnick, M. A. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 3683-3687). This activity requires no nucleotide cofactor but is stimulated more than 10-fold by the addition of yeast single-stranded DNA-binding proteins (ySSBs). In this paper, we describe the aggregation and strand transfer of double-stranded and single-stranded DNA promoted by STP alpha and ySSB. There is a good correlation between the aggregation induced by various DNA-binding proteins (ySSBs, DBPs and histone proteins) and the stimulation of STP alpha-mediated DNA strand transfer. This implies that the stimulation by ySSBs and other binding proteins is probably due to the condensation of single-stranded and double-stranded DNA substrates into coaggregates. Within these coaggregates there is a higher probability of pairing between homologous double-stranded and single-stranded DNA, favoring the initiation of strand transfer. The aggregation reaction is rapid and precedes any reactions related to DNA strand transfer. We propose that condensation into coaggregates is a presynaptic step in DNA strand transfer promoted by STP alpha and that pairing between homologous double- and single-stranded DNA (synapsis) occurs in these coaggregates. Synapsis promoted by STP alpha and ySSBs also occurs between covalently closed double-stranded DNA and single-stranded linear DNA as well as linear double-stranded and linear single-stranded DNAs in the absence of any nucleotide cofactors.
authors.affiliation: Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
authors.forename: R K
authors.initials: RK
authors.lastname: Hamatake
authors.forename: C C
authors.initials: CC
authors.lastname: Dykstra
authors.forename: A
authors.initials: A
authors.lastname: Sugino
mesh_terms: D002384:Catalysis; D004264:DNA Topoisomerases, Type I / Q000502:physiology; D004271:DNA, Fungal / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D004277:DNA, Single-Stranded / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000502:physiology* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000502:physiology* / Q000648:ultrastructure; D008540:Meiosis; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013095:Spermidine / Q000494:pharmacology
chemical_list: D004271:DNA, Fungal; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D004264:DNA Topoisomerases, Type I; D013095:Spermidine