title: Measurement of gene regulation in individual cells reveals rapid switching between promoter states.
abstract: In vivo mapping of transcription-factor binding to the transcriptional output of the regulated gene is hindered by probabilistic promoter occupancy, the presence of multiple gene copies, and cell-to-cell variability. We demonstrate how to overcome these obstacles in the lysogeny maintenance promoter of bacteriophage lambda, P(RM). We simultaneously measured the concentration of the lambda repressor CI and the number of messenger RNAs (mRNAs) from P(RM) in individual Escherichia coli cells, and used a theoretical model to identify the stochastic activity corresponding to different CI binding configurations. We found that switching between promoter configurations is faster than mRNA lifetime and that individual gene copies within the same cell act independently. The simultaneous quantification of transcription factor and promoter activity, followed by stochastic theoretical analysis, provides a tool that can be applied to other genetic circuits.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA. Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, USA.
authors.forename: Leonardo A
authors.initials: LA
authors.lastname: Sepúlveda
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA. Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, USA.
authors.forename: Heng
authors.initials: H
authors.lastname: Xu
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA. Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA. Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, USA. Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Mengyu
authors.initials: M
authors.lastname: Wang
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA. Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, USA. Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030, USA. Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. golding@bcm.edu igolding@illinois.edu.
authors.forename: Ido
authors.initials: I
authors.lastname: Golding
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000821:virology; D018628:Gene Dosage; D005786:Gene Expression Regulation; D008242:Lysogeny / Q000235:genetics; D008962:Models, Theoretical; D011336:Probability; D011401:Promoter Regions, Genetic / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D012097:Repressor Proteins / Q000378:metabolism; D059010:Single-Cell Analysis; D013269:Stochastic Processes; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins