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Science 17 November 2006:
Vol. 314. no. 5802, p. 1045
DOI: 10.1126/science.314.5802.1045g
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This Week in Science

In the initial steps of transcription, RNA polymerase (RNAP) binds to promoter DNA and engages in abortive cycles of synthesis and release of short RNA products until it escapes the promoter and enters processive RNA synthesis. How RNA translocates relative to DNA in the initial transcribing complex has been controversial, with three models proposed (see the Perspective by Roberts). Now two single-molecule studies, one using fluorescence-energy transfer, by Kapanidis et al. (p. 1144), and the other using DNA nanomanipulation, by Revyakin et al. (p. 1139), show that initial transcription involves "scrunching," in which RNAP remains fixed on the promoter and downstream DNA into itself. Accumulated stress from DNA scrunching stress could thus provide the driving force for both abortive initiation and for promoter escape and productive initiation.




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