title: Mechanism of transcriptional bursting in bacteria.
abstract: Transcription of highly expressed genes has been shown to occur in stochastic bursts. But the origin of such ubiquitous phenomenon has not been understood. Here, we present the mechanism in bacteria. We developed a high-throughput, in vitro, single-molecule assay to follow transcription on individual DNA templates in real time. We showed that positive supercoiling buildup on a DNA segment by transcription slows down transcription elongation and eventually stops transcription initiation. Transcription can be resumed upon gyrase binding to the DNA segment. Furthermore, using single-cell mRNA counting fluorescence in situ hybridization (FISH), we found that duty cycles of transcriptional bursting depend on the intracellular gyrase concentration. Together, these findings prove that transcriptional bursting of highly expressed genes in bacteria is primarily caused by reversible gyrase dissociation from and rebinding to a DNA segment, changing the supercoiling level of the segment.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Shasha
authors.initials: S
authors.lastname: Chong
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Chongyi
authors.initials: C
authors.lastname: Chen
authors.affiliation: Biodynamic Optical Imaging Center (BIOPIC), Peking University, Beijing 100871, China; Beijing International Center for Mathematical Research (BICMR), Peking University, Beijing 100871, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Ge
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Biodynamic Optical Imaging Center (BIOPIC), Peking University, Beijing 100871, China. Electronic address: xie@chemistry.harvard.edu.
authors.forename: X Sunney
authors.initials: XS
authors.lastname: Xie
mesh_terms: D027081:DNA Gyrase / Q000378:metabolism; D004278:DNA, Superhelical / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008957:Models, Genetic; D011401:Promoter Regions, Genetic; D061805:Transcription Elongation, Genetic; D061785:Transcription Initiation, Genetic; D014158:Transcription, Genetic
chemical_list: D004278:DNA, Superhelical; D027081:DNA Gyrase