When proteins play tag: the dynamic nature of the replisome.

DNA replication, or the copying of DNA, is a fundamental process to all life. The system of proteins that carries out replication, the replisome, encounters many roadblocks on its way. An inability of the replisome to properly overcome these roadblocks will negatively affect genomic integrity which in turn can lead to disease. Over the past decades, efforts by many researchers using a broad array of approaches have revealed roles for many different proteins during the initial response of the replisome upon encountering roadblocks. Here, we revisit what is known about DNA replication and the effect of roadblocks during DNA replication across different organisms. We also address how advances in single-molecule techniques have changed our view of the replisome from a highly stable machine with behavior dictated by deterministic principles to a dynamic system that is controlled by stochastic processes. We propose that these dynamics will play crucial roles in roadblock bypass. Further single-molecule studies of this bypass will, therefore, be essential to facilitate the in-depth investigation of multi-protein complexes that is necessary to understand complicated collisions on the DNA.