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Molecular Systems Biophysics – From Molecules To Networks 15.01.2019 | 16:45 Uhr - 18:00 Uhr

Biological processes in living cells are tightly controlled. At the nanoscale, however, these processes also follow the laws of statistical physics. Gene expression, the process in which proteins are synthesized from the DNA-encoded information, therefore occurs in bursts, i.e. stochastically in time, which causes variability between individuals. We developed a single-molecule approach that images this bursting in real time in bacterial cells. Despite the fact that all cells are genetically identical, they show largely different bursting dynamics over hours, suggesting weak ergodicity breaking, i.e., the population average differs from the time-average of an individual cell. To understand the molecular origin of gene expression bursts, we combined single-molecule fluorescence tools with cryo-electron microscopy (cryo-EM) to obtain a 3D-model of the protein-DNA complex that initiates gene expression. The model implies an active role of DNA. A structural signal is axially transmitted between two protein binding-sites in the DNA-region that controls gene expression, thus causing an on/off switch in gene activation. This all-or-none behavior is a key component for the robust functioning of genetic networks.

Referent/in

Prof. Dr. Hagen Hofmann, Weizmann Institute of Science, Israel, Department of Structural Biology

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