Fig. 2
From: Structural alteration of DNA induced by viral protein R of HIV-1 triggers the DNA damage response
Vpr induced topological changes on DNA. a Schematic representation of experimental procedure for DNA supercoiling assay. Possible induction of partial unwinding of dsDNA by Vpr induces negative and positive supercoiling (Step-1). In the presence of E. coli Topo1, negative supercoiling (lower side) is relieved by nicking/relegation activity (Step-2). After the de-proteinisation, net amounts of linking number (Lk) are decreased (Step-3). b DNA supercoiling assay with rVpr-Wt. The effects of various amounts of rVpr were tested using E. coli Topo1. OC open circular, RF relaxed form, SC supercoiled. c DNA supercoiling assay with mutants of Vpr. Intensities of each topoisomer were quantified, and their relative amounts are shown in the bottom graph