| Autor: |
Berghuis BA; a Department of Bionanoscience , Kavli institute of Nanoscience, Delft University of Technology , Delft , the Netherlands., Raducanu VS; b Division of Biological and Environmental Science and Engineering , King Abdullah University of Science and Technology , Thuwal , Saudi Arabia., Elshenawy MM; b Division of Biological and Environmental Science and Engineering , King Abdullah University of Science and Technology , Thuwal , Saudi Arabia., Jergic S; c Centre for Medical and Molecular Bioscience , University of Wollongong , Wollongong , New South Wales , Australia., Depken M; a Department of Bionanoscience , Kavli institute of Nanoscience, Delft University of Technology , Delft , the Netherlands., Dixon NE; c Centre for Medical and Molecular Bioscience , University of Wollongong , Wollongong , New South Wales , Australia., Hamdan SM; b Division of Biological and Environmental Science and Engineering , King Abdullah University of Science and Technology , Thuwal , Saudi Arabia., Dekker NH; a Department of Bionanoscience , Kavli institute of Nanoscience, Delft University of Technology , Delft , the Netherlands. |
| Abstrakt: |
Synchronizing the convergence of the two-oppositely moving DNA replication machineries at specific termination sites is a tightly coordinated process in bacteria. In Escherichia coli, a "replication fork trap" - found within a chromosomal region where forks are allowed to enter but not leave - is set by the protein-DNA roadblock Tus-Ter. The exact sequence of events by which Tus-Ter blocks replisomes approaching from one direction but not the other has been the subject of controversy for many decades. Specific protein-protein interactions between the nonpermissive face of Tus and the approaching helicase were challenged by biochemical and structural studies. These studies show that it is the helicase-induced strand separation that triggers the formation of new Tus-Ter interactions at the nonpermissive face - interactions that result in a highly stable "locked" complex. This controversy recently gained renewed attention as three single-molecule-based studies scrutinized this elusive Tus-Ter mechanism - leading to new findings and refinement of existing models, but also generating new questions. Here, we discuss and compare the findings of each of the single-molecule studies to find their common ground, pinpoint the crucial differences that remain, and push the understanding of this bipartite DNA-protein system further. |
