The Conformation Of S-phase chroMOSomes

ended

DNA replication initiation is strictly regulated to ensure complete genome duplication. In eukaryotes, temporal control of origin firing across chromosomes establishes replication timing domains. Failures in the timing of replication initiation across chromosomes is implicated in DNA replication stress, a hallmark of cancer, but the function of these temporally restricted replication domains is not understood. As well as the duplication of DNA, S-phase involves the duplication of all chromosome structural elements and the complete separation of chromosomal intertwines. How this is achieved is poorly understood. A major hurdle for understanding how 3D chromosomal structures are duplicated in S-phase and inherited through mitosis is that current Hi-C methodologies do not give a distinction between chromatids during or immediately after DNA replication. This project aims to visualise the structure and interactions of replicating chromosomes by developing a new Hi-C method which will allow a separate analysis of each new sister chromatid during its formation. This will provide unique information about how DNA loops and interactions are replicated and resolved, preventing the accumulation of toxic chromosomal defects in each new daughter. This method will then be extended to address the impact of replication stress for the inheritance of chromosome structure. The project will result in a new understanding of the interplay of replication timing, DNA damage and chromosome structure, which may provide a novel framework to understand the causes of chromosomal aberrations that accompany tumour progression.