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Tuesday, May 06, 2014

Sharing the Road: Molecular Traffic Jams on DNA

Chemical Biology Chembio Seminar
1640 Chemistry
4:00 PM - 5:30 PM

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Contact:   nwalter@umich.edu
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Speaker:   Ilya Finkelstein, University of Texas Austin
Talk:   SHARING THE ROAD: MOLECULAR TRAFFIC JAMS ON DNA
Abstract:   In the cell, DNA motor proteins act on a crowded DNA track, yet little is known regarding the inevitable collisions that must occur. Using multi-color single-molecule microscopy, we visualized collisions between two model motor proteins and DNA-bound obstacles. We show that both RecBCD, a helicase necessary for initiating homologous DNA recombination, and FtsK, a DNA pump involved in chromosome dimer resolution, actively disrupt nucleoprotein complexes, including RNA polymerase (RNAP) holoenzyme. Surprisingly, FtsK can push, evict, and even bypass DNA-bound proteins. The primary factor dictating the outcome of collisions was the relative affinity of the proteins for their specific binding sites. Importantly, protein-protein interactions between FtsK and XerD help prevent removal of XerCD from DNA by promoting rapid reversal of FtsK. Finally, we demonstrate that RecBCD always overwhelms FtsK when these two motor proteins collide while traveling along the same DNA molecule, indicating that RecBCD is capable of exerting a much greater pushing force than FtsK when translocating along DNA.