Single strand annealing and ATP-independent strand exchange activities of yeast and human DNA2: possible role in Okazaki fragment maturation |
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Authors: | Masuda-Sasa Taro Polaczek Piotr Campbell Judith L |
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Institution: | Braun Laboratories, California Institute of Technology, Pasadena, CA 91125, USA. |
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Abstract: | The Dna2 protein is a multifunctional enzyme with 5'-3' DNA helicase, DNA-dependent ATPase, 3' exo/endonuclease, and 5' exo/endonuclease. The enzyme is highly specific for structures containing single-stranded flaps adjacent to duplex regions. We report here two novel activities of both the yeast and human Dna2 helicase/nuclease protein: single strand annealing and ATP-independent strand exchange on short duplexes. These activities are independent of ATPase/helicase and nuclease activities in that mutations eliminating either nuclease or ATPase/helicase do not inhibit strand annealing or strand exchange. ATP inhibits strand exchange. A model rationalizing the multiple catalytic functions of Dna2 and leading to its coordination with other enzymes in processing single-stranded flaps during DNA replication and repair is presented. |
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