Fig. 4
From: Promotion of homology-directed DNA repair by polyamines
Polyamines enhance duplex capture and synaptic complex formation by RAD51. a Schematic of the duplex capture assay. b Duplex DNA capture by the RAD51 presynaptic filament was examined without or with spermidine. Note that AMP-PNP was used as the nucleotide cofactor to assemble a stable RAD51 nucleoprotein filament. c Schematic of the synaptic complex assay. Briefly, RAD51 presynaptic filament was incubated with duplex DNA containing either homology or non-homology of the restriction enzyme cutting site (SspI or AflIII) and then challenged with the indicated restriction enzyme (SspI herein or AflIII in Supplementary Fig. 9f). d Synaptic complex assembly by the RAD51 presynaptic filament was examined without or with spermidine. Following SspI digestion, the DNA species were resolved by agarose gel electrophoresis and stained with ethidium bromide. e Model depicting the mechanistic action of polyamines in promoting RAD51-mediated recombination. Three possible effects of polyamines in facilitating RAD51-mediated DNA strand exchange. i Polyamines promote the interaction between RAD51-ssDNA filament and duplex DNA. ii Polyamines could stabilize the invading ssDNA with the complementary ssDNA strand in the homologous duplex target during strand exchange. iii DNA condensation mediated by polyamines may facilitate intersegmental contact sampling33 by RAD51 filament during homology search. Data are the mean ± s.e.m. from three independent experiments (n = 3). Source data are provided as a Source Data file
