The replicative helicase MCM2-7 vs. the genome: A genomic obstacle run to keep us healthy
Our main model organism used in the lab is the budding yeast Saccharomyces cerevisiae, which has been used for thousands of years to produce goods such as bread and beer.
We utilise this unicellular organism to investigate how DNA is replicated. The main reasons being its fast growth, genetical accessibility, fully sequenced genome and the unique fact that the locations, where DNA replication begins are defined by genetic elements called origins of replication. |
DNA replication is the complex process that allows every living cell to faithfully duplicate their genome before cell division. From small genomes (E. coli bacterium, 4.6 million base pairs ) to larger (human cells, approx. 6.3 gigabase pairs), DNA replication has to ensure that the whole DNA content is copied precisely and in time. Therefore, multiple replication forks are propelling through the bigger genomes to fulfill that duty. At the heart of the replication fork is the ring-shaped, replicative helicase MCM2-7 complex (Mini chromosome maintenance 2-7), which unwinds the double-stranded DNA like a molecular zipper and feeds it to the DNA polymerases. These very accurate enzymes then copy the DNA in a semi-conservative manner to yield two double-stranded copies of the genome.
The replicative helicase has its own loader, called Origin recognition complex (ORC), which loads two copies of the helicase in a head-to-head conformation onto origin DNA once every cell cycle (G2/M until late G1). When the cell commits to DNA replication in S-phase, this MCM2-7 dimer gets activated, splits and each produces a replication fork. |
Having a background in gene expression i.e., the complex process that reads the information encoded in the genome to produce RNA and eventually proteins, as well as in DNA replication, I am now focusing my research on 1) the intersection of these processes i.e., when these two DNA-bound and travelling machineries collide; and 2) on how the replication machinery, and more specifically, the MCM2-7 replicative helicase copes with obstacles and DNA damage. Here, I have identified a novel candidate that could alleviate replication stress by promoting MCM2-7 activity/ processivity at sites of insults, e.g. transcription-replication conflicts, non-B DNA structures, or various DNA damages. Using an exclusively-available chemical-biology approach allows us to investigate the MCM2-7 complex in vivo at unprecedented details and resolution.
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Recently, we are also expanding our research in a collaborative approach to understand DNA replication in higher eukaryotes. Here, the ultimate goal is to define the origins of replication as well as the proteins involved in human cell lines. In particular, we want to understand how and where replication complexes are loaded onto DNA prior to S-phase and if this can be targeted for therapeutic purposes in the future.
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