R-loop formation in trans detected by radiolabeling of the transcript. (a) Agarose gel stained with ethidium bromide and (b) autoradiogram of the same gel. Lane 1: pBluescript SK linearized with Xba I; lane 2: supercoiled pHC624-(AGGAG)22; lane 3: pHC624-(AGGAG)22 linearized with Sca I; lane 4: pSK-(AGGAG)22 linearized with Xba I; lane 5: linearized pSK-(AGGAG)22 and supercoiled pHC624-(AGGAG)22; and lane 6: linearized pSK-(AGGAG)22 and linearized pHC624-(AGGAG)22. All DNAs were incubated in the transcription mixture with T7 RNA polymerase.
