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Transcribing SupercoilsThis image of RNA polymerase transcribing supercoils was created by Nello Bossi.
You can download the original quicktime movie from here in BinHex format.
Rob Edwards also created two animated gif images from the original. The faster image has a frame delay of 0.1 secs and is essentially the same as the movie, and the slower image has a frame delay of 0.5 secs. Both should be displayed in your browser.
This is the original description from Nello:
Dear friends & colleagues We thought that you might like viewing the attached document: a short animated sequence - a "Quicktime" movie (our apologies to non-Mac users) - portraying a model (yes, a model) of how RNA polymerase could manage to read a double stranded helical template (often negatively supercoiled) without the nascent RNA becoming irremediably entangled around the DNA. [We remind you that the displacement of the transcription bubble along the template requires rotation of the bubble around the template axis]. The model proposes that binding of RNA polymerase to the promoter and formation of the transcription bubble "inoculates" the formation of a plectonemic supercoiled branch that extrudes as transcription goes on. Maintenance of an apical position by RNA polymerase prevents RNA/DNA entanglement. The movie is largely inspired by the electron micrographs of ten Heggeler-Bordier et al. EMBO J 11, 667-672 (1992). In the animated sequence, the template is a small negatively supercoiled circular DNA molecule. The transcribed region spans roughly one-fourth of the circle. You have the right to three complete transcription cycles (those of you who have a QuickTime Movie Player application with a "loop" function available, can have it running indefinitely). NelloNote that this page moved recently. You should update your bookmark, although the old one should automatically forward you here