Figure 4.

(a) and (b). Time-course strand transfer assay shows that strand transfer is involved in the synthesis of long DNA products. (a) A schematic diagram of the strand transfer assay is shown. The RNA (continuous lines) without the dimer signal was used as the donor and was hybridized to a 20 nt 5′ ³²P-labeled DNA (broken lines) primer. A longer RNA without the binding site for the donor primer was used as acceptor. Full extension on the donor produced a 1394 nt DNA while transfer and subsequent extension on the acceptor produced a 1538 nt product. The region of homology (homologous transfer zone) between the donor and acceptor is boxed. (b) An autoradiogram of a strand transfer experiment. The reactions were carried out in the presence of 4 μM NC for time points 2, 5, 10, 15, 30, 45, 60 and 75 min as shown from left to right. In the last lane (*), the reaction was carried out by adding excess donor RNA to the reaction instead of acceptor RNA and this reaction was carried out for 75 min. The positions of full-length DNA products from the donor (1394) or transfer products (1538) are indicated. Other markings are as in Figure 1(b). A repeat experiment yielded similar results.