Fig. 1.

Rad51 and Rad54 generate complement-stabilized D-loops. (A) Schematic representation of cs-D-loop formation. (I) Rad51 and Rad54 promote D-loop formation. (II) Single D-loops are unstable upon restriction. (III) The single D-loop can be stabilized by pairing the displaced strand in the D-loop with a complementary oligonucleotide. (IV) This complement-stabilized D-loop is stable upon restriction. Red star indicates position of ³²P label on the 5′ ends of ssDNA. (B) D-loops and cs-D-loops were formed as described in Materials and Methods and analyzed by electrophoresis. Lane 1, single D-loops; lane 2, single D-loops treated with HindIII; lane 3, cs-D-loops; lane 4, cs-D-loops treated with HindIII. The positions of D-loops, cs-D-loops, free oligonucleotides, and molecular size markers (kbp) are indicated. (C) The order of oligonucleotide addition was interchanged; lanes are as in B. The amounts of cs-D-loops formed in lane 4 of B and C were 3 ± 0.5% and 1.2 ± 0.3%, respectively, expressed relative to the scDNA concentration that is limiting; error is the SEM.