RNA Polymerase Rotates DNA during Transcription
  









  







  




View from above.  Playback at twice the original speed.
  







  
  
RNA polymerase is a molecular machine that reads the genetic code on a DNA molecule and transcribes it onto a messenger RNA.  In doing so, RNA polymerase rotates DNA, as seen in the movie on the right.  The right-handed double helix of DNA passes through the RNA polymerase as if a right-handed screw goes through its mate nut.
(To observe rotation, we attached a magnetic bead to the tail end of DNA and pulled the bead upward with a magnet.  A small fluorescent bead served as a makder of rotation.)
  
                                                            Harada, Y. et al., Nature 409, 113-115 (2001).