Scott Berger


“Orchestrating a Molecular Symphony: Single-Molecule Imaging of Animal DNA Replication Initiation”

At all stages in our life cycle, our genome is replicated from ten thousand or more sites called origins. Bidirectional replication, the process in which two replisomes are assembled and begin replicating DNA in opposite directions, occurs with incredibly high fidelity. The error rate for assembling only one replisome at an origin, termed unidirectional replication, must be less than one in ten million. As the replisome is a complex molecular machine which dates to the last common ancestor of all life, understanding the mechanism is of paramount fundamental importance. My colleagues and I have shown two essential subunits of the replicative helicase are recruited in pairs from solution using real-time single-molecule imaging in Xenopus egg extracts. The simultaneous assembly of both helicases in distinct steps provides an intuitive mechanism to ensure bidirectional replication.


Animals exhibit exquisite fidelity in initiating DNA replication bidirectionally, that is, with two replisomes travelling in opposite directions from a single origin. Using single-molecule microscopy, I study how animals enforce the robust assembly and activation of two replisomes at one place and time.

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