Human meiotic recombinase Dmc1 promotes ATP-dependent homologous DNA strand exchange


Homologous recombination is crucial for the repair of DNA breaks and maintenance of genome stability1,2,3. In Escherichia coli, homologous recombination is dependent on the RecA protein. In the presence of ATP, RecA mediates the homologous DNA pairing and strand exchange reaction that links recombining DNA molecules. DNA joint formation is initiated through the nucleation of RecA onto single-stranded DNA (ssDNA) to form helical nucleoprotein filaments4,5,6. Two RecA-like recombinases, Rad51 and Dmc1, exist in eukaryotes1. Whereas Rad51 is needed for both mitotic and meiotic recombination events, the function of Dmc1 is restricted to meiosis3,7. Here we examine human Dmc1 protein (hDmc1) for the ability to promote DNA strand exchange, and show that hDmc1 mediates strand exchange between paired DNA substrates over at least several thousand base pairs. DNA strand exchange requires ATP and is strongly dependent on the heterotrimeric ssDNA-binding molecule replication factor A (RPA). We present evidence that hDmc1-mediated DNA recombination initiates through the nucleation of hDmc1 onto ssDNA to form a helical nucleoprotein filament. The DNA strand exchange activity of hDmc1 is probably indispensable for repair of DNA double-strand breaks during meiosis and for maintaining the ploidy of meiotic chromosomes.

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Figure 1: hDmc1 catalyses ATP-dependent DNA strand exchange.
Figure 2: Dependence of hDmc1-mediated DNA strand exchange on hRPA and salt.
Figure 3: hDmc1 mediates robust D-loop formation.
Figure 4: Analysis of hDmc1-ssDNA complexes by electron microscopy.


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We thank T. Habu for helping with cDNA cloning and baculovirus construction. This work was supported by grants from the US National Institutes of Health (P.S. and V.M.U.).

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Correspondence to Patrick Sung.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Figure 1

DNA strand exchange reactions that used the 3' and 5' end-labeled duplex molecules. (JPG 30 kb)

Supplementary Figure 2

This figure shows a physical and functional interaction of Rad54B with hDmc1. (JPG 43 kb)

Supplementary Information

Methods and legends for Supplementary Figures 1 and 2. (DOC 33 kb)

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Sehorn, M., Sigurdsson, S., Bussen, W. et al. Human meiotic recombinase Dmc1 promotes ATP-dependent homologous DNA strand exchange. Nature 429, 433–437 (2004).

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