Abstract
The eukaryotic cell cycle coordinates the accurate duplication and segregation of the genome during proliferation. The large genomes of eukaryotic cells are replicated from multiple replication origins during S phase. These origins are not activated synchronously at the beginning of S phase, but instead fire throughout S phase according to a pre-determined, cell type specific program. Ensuring that each origin is efficiently activated once and only once during each S phase is crucial for maintaining the integrity of the genome. This is achieved by a two-step mechanism. The first step, known as licensing, involves the loading of the MCM2-7 proteins into pre-replicative complexes (pre-RCs) at origins. In the second step, the MCM helicase is activated by a large set of ‘firing factors’. These two steps are differentially regulated by cyclin dependent kinase (CDK): licensing is inhibited by CDK, whilst firing requires CDK. As a consequence, licensing can only happen during G1 phase, when CDK activity is low, and origin firing cannot occur during G1 phase.
The speaker has recently described the reconstitution of yeast DNA replication with purified proteins. In this lecture, he will present recent results using this system to study chromatin replication and replication through protein obstacles.
About the speaker
Dr John Diffley obtained his PhD from New York University in 1985, and was a Postdoctoral Fellow at Cold Spring Harbor Laboratory until 1990. He continued his research at the Clare Hall Laboratories, where he became the Director in 2006. In the same year he was appointed the Deputy Director of the London Research Institute, and became the Associate Research Director at the Francis Crick Institute in 2015.
Dr Diffley’s research focuses on the use of genetics, biochemistry, molecular and cellular biology to elaborate the events that occur at origins of eukaryotic DNA replication throughout the cell cycle. His most significant contribution was the discovery and characterization of the pre-replicative complex (pre-RC), which contains the origin recognition complex (ORC), Cdc6 and the Mcm2-7 complex. His laboratory showed that cyclin-dependent kinases prevent pre-RC assembly in budding yeast by inhibiting ORC, and by regulating Cdc6 proteolysis and Mcm2-7 nuclear localization.
Dr Diffley received numerous awards including the Louis-Jeantet Prize for Medicine (2016) and the Paul Marks Prize for Cancer Research (2003). He was elected as a Member of the European Molecular Biology Organization (EMBO), as well as a Fellow of the Royal Society, of the American Association for the Advancement of Science, of the Academia Europaea, of the Academy of Medical Sciences and of the European Academy of Cancer Sciences.
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