the measure of dynamics and molecular interactions, the analysis of cellular complexes assembly in living cells in response to environmental changes, constitute a major stake in biology. In this context, the regulation of gene activity is a complex task and represents a sound model to develop new computing technologies. Deciphering the dynamics of transcription factors (TFs) is essential to understand how the genetic expression is regulated in the cell nucleus and more specifically the role of this dynamics in the identification of target genes by TFS. Classically, TFs display a subdiffusive behavior which can be modelled with an anomalous diffusion. Yet the underlying physical mechanisms involved are still debated. A high molecular crowding is often used to explain the anomalous diffusion of TFs in the cell nucleus. However, interactions of TFs with specific partners of interest is also likely to account for the anomalous diffusion we observe. To address these questions, we focus our work on the mechanisms associated with the transcriptional pause release, involving a complex known as the P-TEFb complex (positive transcription elongation factor). This mode of regulation is highly conserved through evolution. We have developed different microscopy-based strategies to measure the dynamics and molecular interactions in living cells (based on FLIM/FRET and FCS or single molecule tracking). We have combined these complementary technics to study spatiotemporal events. I will present how we have integrated the different types of information we have obtained to get a better view of the dynamic of the P-TEFb complex in transcription pause release.

Contact : karin.sadoul@univ-grenoble-alpes.fr