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A Recombinase from Drosophila melanogaster Embryos
Andrew Eisen and R. Daniel Camerini-Otero
Proceedings of the National Academy of Sciences of the United States of America
Vol. 85, No. 20 (Oct. 15, 1988), pp. 7481-7485
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/32967
Page Count: 5
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We have partially purified a DNA strand-exchange activity (recombinase) from nuclear extracts of Drosophila melanogaster embryos. The protein fraction forms a joint molecule between a circular single-strand DNA and a homologous linear duplex DNA that is resolved from the substrates by agarose gel electrophoresis. A strand-exchange activity can be obtained from nuclear extracts from embryos as old as 24 hr. The activity is similar to that partially purified from human cells [Hsieh, P., Meyn, S. M. & Camerini-Otero, R. D. (1986) Cell 44, 885-894]. It is homology-dependent, requires Mg2+, appears to be directional in that it prefers to displace the 3′ end of the noncomplementary strand, and does not require exogenous ATP. Forty nanograms of protein in the partially purified DNA strand-exchange fraction from D. melanogaster embryos can completely convert 50 ng of substrate single-strand DNA into joint molecules in 10 min. In the electron microscope, joint molecules are seen to consist of a circular single-strand DNA molecule attached to only one end of a linear duplex DNA molecule; a displaced strand is also seen. The region of heteroduplex formation can be as long as 600 base pairs. The demonstration of a strand-exchange activity from wild-type D. melanogaster embryos invites analysis of recombination-defective mutants to explore the role of DNA strand exchange in homologous recombination.
Proceedings of the National Academy of Sciences of the United States of America © 1988 National Academy of Sciences