The human homologous pairing protein HPP-1 is specifically stimulated by the cognate single-stranded binding protein hRP-A.
Homologous pairing and strand exchange of DNA are catalyzed by the human homologous pairing protein HPP-1 in a magnesium-dependent, ATP-independent reaction that requires homologous DNA substrates and stoichiometric quantities of HPP-1. Here we show that the addition of the purified human single-strand binding (SSB) protein hRP-A to the reaction mixture stimulates the rate of homologous pairing 70-fold and reduces the amount of HPP-1 required for the reaction at least 10-fold. The identification of hRP-A as a stimulatory factor of HPP-1-catalyzed reaction was facilitated by its recognition as a member of a high molecular weight complex of recombination components. Neither the Escherichia coli SSB protein, bacteriophage T4 gene 32 protein, nor the highly conserved Saccharomyces cerevisiae yRP-A SSB protein could substitute for hRP-A in this stimulation. Because only the cognate SSB was capable of stimulating HPP-1, these results suggest that eukaryotes depend on unique and specific interactions between DNA recombination components.
Laboratory of Chromosome Biology, National Cancer Institute-Frederick Cancer Research and Development Center, MD 21702.
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D015153:Blotting, Western; D002850:Chromatography, Gel; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D011995:Recombination, Genetic; D051716:Replication Protein A
D004268:DNA-Binding Proteins; D011506:Proteins; C497167:RPA1 protein, human; D011994:Recombinant Proteins; D051716:Replication Protein A