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Sensitive homologous recombination strand-transfer assay: partial purification of a Drosophila melanogaster enzyme and detection of sequence effects on the strand-transfer activity of RecA protein

McCarthy, J.G.; Sander, M.; Lowenhaupt, K.; Rich, A.

Proceedings of the National Academy of Sciences of the United States of America 85(16): 5854-5858

1988


ISSN/ISBN: 0027-8424
PMID: 3137561
DOI: 10.1073/pnas.85.16.5854
Accession: 041329651

A sensitive homologous recombination strand-transfer assay is described that employs short radiolabeled double-stranded DNA fragments from the lac/polylinker region of plasmid pUC18 and (+)viral M13mp18 single-stranded DNA as substrates. Substitution of a short radiolabeled double-stranded fragment for full-length linear M13 double-stranded DNA results in an assay whose sensitivity is improved greater than 8-fold. In addition, it is less sensitive to interference from nucleases or ligases than previous assays. The assay was used to partially purify an ATP-independent strand-transfer activity from a crude nuclear extract of Drosophila melanogaster embryos. We have also tested the efficiency with which various short double-stranded DNA segments are assembled into plectonemic joints by RecA protein with this assay and found 5- to 10-fold differences. These results are interpreted as evidence for DNA sequence-specific effects in RecA-mediated homologous pairing in vitro.

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