CoSMoS unravels mysteries of transcription initiation

Abstract

Using a fluorescence method called colocalization single-molecule spectroscopy (CoSMoS), Friedman and Gelles dissect the kinetics of transcription initiation at a bacterial promoter. Ultimately, CoSMoS could greatly aid the study of the effects of DNA sequence and transcription factors on both prokaryotic and eukaryotic promoters.

Figure 1. Transcription Initiation at a σ⁵⁴-Dependent Promoter

Rates are shown for individual steps as deduced by CoSMoS analysis (Friedman and Gelles, 2012). Promoter DNA and RNA polymerase (blue, with σ in yellow) come together to form two sequential closed complexes. Closed complex 2 then isomerizes into an open complex in which the DNA bends toward the active site and forms a single-stranded bubble surrounding the transcription start site. Finally, as the enzyme escapes the promoter, an RNA chain (red) is synthesized, σ is released, and the elongation complex forms.