Dancing proteins filmed on densely covered DNA
Research into life in the cell now more realistic thanks to new microscope
Researchers from the FOM Foundation and the VU University Amsterdam are the first to have made a live film about how proteins dance over densely covered DNA. For this they worked together with German colleagues to develop a unique microscope that can grasp and stretch DNA and then film it in unrivalled detail. This development is important for a better understanding of living processes in our cells where DNA is always densely covered with proteins. Examples include essential processes such as the copying and repair of DNA. The results were published this week as the cover article in the scientific journal Nature Methods.
Naked DNA does not exist
Naked DNA, as it is usually portrayed , does not exist in our cells. Countless proteins are constantly trying to obtain a spot on the DNA to perform their preprogrammed tasks. These tasks – varying from the copying of DNA during cell division to the repair of DNA if it is damaged – are essential for cell function and for preventing cell disease and death. The realisation of these tasks is , however , limited by the busyness on the DNA. Consequently if we are to gain a good understanding of life in our cells then we must also be able to study DNA under such busy conditions in the lab .
Microscopic 'hands' and superresolution 'eyes'
Up until now limitations in microscopy meant that scientists could only film proteins on DNA that was more or less naked. But now thanks to two tricks they can film DNA under realistic busy conditions. The first trick involves optical tweezers: these are strong lasers – microscopic hands so to speak – with which you can grab the two ends of a DNA strand, stretch out the DNA and hold it still. The second trick involves superresolution: this is a major breakthrough in light microscopy as a result of which you can still see – as if you had superfocused vision – the individual proteins dancing over the stretched out DNA even if it is very busy .
Reference
Iddo Heller, Gerrit Sitters, Onno D . Broekmans, Géraldine Farge, Carolin Menges, Wolfgang Wende, Stefan W. Hell, Erwin J.G. Peterman & Gijs J.L. Wuite. STED nanoscopy combined with optical tweezers reveals protein dynamics on densely covered DNA. Nature Methods (2013).
Further information
The article has been published in the September edition of Nature Methods and the research was partly funded by FOM. For further information please contact Iddo Heller or Gijs Wuite.