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The Houtsmuller Group

In vivo dynamics and reaction kinetics of nuclear processes

The regulation and structural requirements of vital nuclear processes such as DNA replication, transcription, RNA processing and DNA repair inside the eukaryote nucleus are poorly understood. Engagement of nuclear proteins in these processes requires transport of the involved proteins to their sites of activity (e.g. DNA-damage or specific base pair sequences). At those sites, proteins or precursor complexes are assembled into large DNA-protein holo-complexes for at least the time of their action. Limited knowledge exists about the nature and timing of these events, about the composition of precursor-complexes and about the mode and efficiency of their transport to specific sites.

Our aim is to unravel the dynamics of macromolecular interactions required for these nuclear processes in living cells. We study the mobility and reaction kinetics in living cells of proteins involved in

   1. transcription regulation by steroid hormones (androgen receptors) and basal transcription factors (TFIIH),
   2. DNA maintenance processes including nucleotide excision repair (NER), double strand break repair mechanisms (in close collaboration with researchers of the Department of Cell biology and Genetics) and telomere maintenance (in close collaboration with the Hematology Deparment)

We use fluorescent proteins (GFP, CFP, YFP) to tag repair and transcription factors and study their mobility and the kinetics of the processes they are involved in by confocal microscopy, fluorescence recovery after photobleaching (FRAP) and fluorescence correlation spectroscopy (FCS). In addition, we have developed a computer modeling environment to simulate the various FRAP and FCS procedures with the aim to accurately quantify the FRAP experiments, taking into account the many deviations from theoretical models that occur in practice in these types of experiments.