Date: 09.02.2023, Time: 15:30h

Location: Kleiner Physikhörsaal N020, Faculty of Physics
The talk will also be streamed online.

Dr. Ferdinand Greiss
Weizmann Institute of Science

An artificial cell responds to environmental selective pressure by point mutations on a single DNA molecule. As the long-standing vision for constructing such evolving artificial cells, we are exploring ways to engineer minimal genetically encoded systems from single DNA molecules with cell-free gene expression. We studied genetic decision-making with different effective noise levels through high (~10⁶) and low (~10) numbers of DNA molecules in microfluidic cell-like compartments. Decision-making near the switching point showed critical slowing-down, with fast fuzzy switching at low numbers and slow precise switching at high numbers. We realized a rapid fluorescent reporter system to directly observe coupled transcription and translation through nascent proteins tethered to a gene by transient RNA polymerase-mRNA-ribosome complexes. We found proteins emerging in bursts, an expected consequence of transcriptional-induced supercoiling. With this co-expressional localization of proteins and DNA, we found nascent regulatory proteins can regulate genes on the same DNA molecule, even without the confinements of a cell far below concentrations for equilibrium binding. We rationally built a pulsatile genetic circuit from a genetically encoded activator and repressor in feedback on the same DNA molecule. The cell-free genetic circuit was driven by only a handful of proteins per gene and hour, showing variability in the ensemble of DNA molecules. Taken together, we are approaching the level of control over minimal genetic systems where we can tackle the construction of evolving artificial cells based on single DNA molecules.