Title: Magic Tricks of Multi-protein Machineries: How proteins fold DNA and load onto DNA through action over distance

Abstract: Our lab applies single-molecule imaging techniques to address unanswered questions regarding key biological pathways. Especially, the recent development of single-molecule imaging techniques enables us to observe real-time dynamics of protein-DNA interactions with high spatial and temporal resolutions. This talk will focus on protein complexes involved in 1) telomere maintenance, 2) 3D chromatin organization, and 3) mitochondrial DNA replication. Firstly, recent studies from our lab demonstrate how proteins form higher-order DNA structures, such as DNA-DNA bridging and T-loops at telomeres. Secondly, the cohesin complex was proposed to mediate 3D chromatin structures through DNA loop extrusion. However, its mechanism of action is still largely unknown. Our results from using High-speed AFM imaging of the cohesin-DNA complex support a tethered-inchworm DNA loop extrusion model. Lastly, mitochondrial DNA helicase Twinkle forms hexametric rings; how this protein self loads onto DNA was unknown. Using High-speed AFM imaging, we, for the first time, captured in real-time how a ring-shaped helicase loads onto its DNA. A domain of Twinkle can protrude ~5 nm away from Twinkle to capture DNA in proximity and bring it to the helicase central channel for loading. 

Host: Thomas Schäefer