Hocine Mankouri – University of Copenhagen

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CCS > Research > Hocine Mankouri

Hocine Mankouri

Research interests

“DNA replication stress” is caused by defects in normal replication fork progression and is a major threat to genome stability. It is a commonly observed feature of cancer cells, and also implicated as a driving force for age-associated functional decline in certain cell types. Our primary research interests are to characterise the molecular events that occur following site-specific DNA replication fork perturbation, and determine how these events impact upon general cell physiology and ageing. Much of our research utilizes the model organism, budding yeast, which allows us to combine molecular genetics with the analysis of DNA replication at defined loci. Key findings in yeast will then be directly extrapolated to mammalian systems.

Our key roles within the CCS are:
1) To use and develop novel innovative methodologies (e.g. The Tus-Ter barrier; Figure 1) to detect and characterise site-specific stalled replication forks in vivo.

2) To characterise DNA replication defects occurring in yeast models of human genetic instability disorders (e.g. the yeast sgs1 mutant, which lacks a conserved RecQ helicase that is mutated in the cancer-prone disorder, Bloom’s syndrome).

3) To understand how chromosome instability is counteracted at naturally difficult-to-replicate sites in the genome (e.g. telomeres, and late-replicating sequences).

4) To analyse how under-replicated, or incompletely processed, regions of the genome that are carried-over into mitosis can interfere with subsequent chromosome segregation events.

Figure 1. Using the E. coli Tus-Ter barrier to site-specifically stall replication forks.
Tus is a small monomeric protein that binds to specific 21-bp DNA sequences called Ter. Tus-Ter functions as a polar replication fork barrier in E. coli and is utilized to induce site-specific DNA replication termination in that organism. The Tus-Ter complex does not exist in eukaryotes, but a number of recent studies have demonstrated that it can be used as a novel tool to study site-specific DNA replication perturbation when reconstituted in eukaryotic genomes. In yeast, the Tus-Ter complex retains its intrinsic polarity and blocks DNA replication forks only when it is orientated in the so-called “Restrictive” orientation (rather than the control “permissive” orientation). We aim to utilise this versatile system to create specific types of DNA replication problems (e.g. under-replicated regions of the genome) that can be studied at the level of a defined locus.

 

Relevant Publications

Mankouri H. W., Ashton, T. M., and Hickson I. D. (2011). Holliday junction-containing DNA structures persist in cells lacking Sgs1 or Top3 following exposure to DNA damage. Proceedings of the National Academy of Sciences 108 (12), 4944-9.

Mankouri, H. W., Huttner, D. and Hickson I. D. (2013). How unfinished business from S-phase affects mitosis and beyond. The EMBO Journal 32 (20), 2661-71.

Larsen, N. B., Sass, E., Suski, S., Mankouri, H. W.* and Hickson I. D.* (2014).  The Escherichia coli Tus-Ter replication fork barrier causes site-specific DNA replication perturbation in yeast. Nature Communications 5:3574 doi: 10.1038/ncomms4574
(* Co-corresponding authors)

Tus-Ter as a tool to study site-specific DNA replication perturbation in eukaryotes. Larsen, N. B., Hickson, I. D. and Mankouri H. W. (2014). Cell Cycle 13 (19), 2994-2998.