Journal: Methods in enzymology
Article Title: Single-Stranded DNA Curtains for Studying Homologous Recombination
doi: 10.1016/bs.mie.2016.08.005
Figure Lengend Snippet: RPA-coated ssDNA curtains. (A) Wide-field TIRFM image of a double-tethered ssDNA curtain bound by RPA-eGFP. (B) Kymograph showing what takes place when single-tethered ssDNA molecules are labeled with RPA-eGFP. The ssDNA slowly becomes longer as RPA-eGFP binds and disrupts existing secondary structure. (C) Kymograph showing facilitated dissociation of RPA from the ssDNA when free RPA is injected into the sample chamber. RPA-eGFP is shown in green, and RPA-mCherry is shown in magenta, and the color-coded arrowheads indicate successive injections of each protein. (D) Kymographs of a single-tethered ssDNA showing that the exchange of wild-type RPA-eGFP with wild-type RPA-mCherry does not alter ssDNA length (upper panel), whereas exchange of the RPAt48 mutant, which is defective for ssDNA binding, with wild-type RPA-mCherry coincides with an increase in ssDNA length. Adapted with permission from Deng, S. K., Gibb, B., de Almeida, M. J., Greene, E. C., & Symington, L. S. (2014). RPA antagonizes microhomology-mediated repair of DNA double-strand breaks. Nature Structural and Molecular Biology, 21, 405–412; Gibb, B., Silverstein, T. D., Finkelstein, I. J., & Greene, E. C. (2012). Single-stranded DNA curtains for real-time single-molecule visualization of protein-nucleic acid interactions, Analytical Chemistry, 84, 7607–7612; Gibb, B., Ye, L. F., Gergoudis, S. C., Kwon, Y., Niu, H., Sung, P., et al. (2014). Concentration-dependent exchange of replication protein A on single-stranded DNA revealed by single-molecule imaging. PloS One, 9, e87922; Gibb, B., Ye, L. F., Kwon, Y., Niu, H., Sung, P., & Greene, E. C. (2014). Protein dynamics during presynaptic-complex assembly on individual single-stranded DNA molecules. Nature Structural and Molecular Biology; and Qi, Z., Redding, S., Lee, J. Y., Gibb, B., Kwon, Y., Niu, H., et al. (2015). DNA sequence alignment by microhomology sampling during homologous recombination. Cell, 160, 856–869.
Article Snippet: Preparation of ssDNA Our ssDNA curtain experiments make use of relative long ssDNA substrates (≥40,000 nucleotides) that are made by rolling circle replication with a biotinylated oligonucleotide primer and a circular ssDNA template ( Gibb et al., 2012 ), as described later. list-behavior=enumerated prefix-word= mark-type=decimal max-label-size=0 The biotinylated primer is first annealed to a circular M13 DNA template in a 100-μL reaction containing: 40 m M Tris-HCl [pH 8.0], 50 m M NaCl, 10 m M MgCl 2 , 10 μg (89.4 n M ) of M13mp18 (New England Biolabs, Cat. No. N4040S), and 45 n M primer (5′-BIO-TEG-TTT TTT TTT TTT TTT TTT TTT TTT TTT TTT GTA AAA CGA CGG CCA GT).
Techniques: Labeling, Injection, Mutagenesis, Binding Assay, Concentration Assay, Imaging, Sequencing, Sampling, Homologous Recombination