Real time in situ chromatin dynamics tracking at nanoscale resolution during transcription activation in human cells
Léa Costes, Martin Rey-Millet, Manoel Manghi, Kerstin Bystricky
Center for Integrative Biology (CBI), Molecular, Cellular and Developmental biology unit (MCD) and Laboratory for Theoretical Physics (LPT), University of Toulouse Paul Sabatier, CNRS, Toulouse, France
The three-dimensional organization of the genome orchestrates gene expression but ‘what comes first’ between reaction to transcription and contribution to proper function is a matter of debate. We develop live cell fluorescence imaging methodologies to investigate how dynamic changes in chromatin organization respond to and participate in regulation of transcription activation and external insults. Real-time whole genome nanoscale tracking (HiD) of DNA and transcription factors combined with numerical polymer modeling and chromatin conformation capture techniques provide insights into the mechanisms by which transcription activation rapidly confines motion and reorganizes pre-existing domain folding. Random Illumination Microscopy (RIM) provides exquisite resolution and detail of these processes.
We analyze how transcription initiation modulates chromatin locally within minutes and accompanies processive transcription due to RNA polymerase II induced forces. At the level of the whole nucleus, confined motion predominates in dynamic regimes of both chromatin and of transcription factors. The link between transcriptional activity, domain folding, frequencies of long and short range contacts and real time dynamics, will be discussed.