Fig. 3

A detailed process of BS-based template switching interpreting HIV-1 homologous recombination. a RT encounters a BS during reverse transcription. Then, a “climb process” occurs. b When RT “climbs up” and transfers to the acceptor template, the realignment of the nascent DNA strand onto the acceptor template via base pairing behind the growing site would modulate forward direction of RT as a tadpole changes its direction by modulating the azimuth of its tail. This action would prevent RT from proceeding on in the initial direction, and adjust RT to advance along acceptor template. c Concomitantly, the already formed BS would be released more easily. The sway of two gRNA strands as well as the nascent DNA is inevitable under the kinetic actions. Therefore, losing the balance due to RNase H-mediated degradation, the donor template would readily dissociate with the acceptor template and the nascent DNA, resulting in the resolution of the BS. Unable to return to the donor template, RT “has to” continue the following synthesis along the acceptor template. d Finally, a successful homologous template switching is completed. The thin linear arrows indicate the direction of DNA synthesis. The arc arrows indicate the sway of the donor template