Dicentric prevention and resolution – DICENs

Using advanced yeast molecular genetics and cell biology approaches, we have developed highly sensitive and quantitative assays to detect the formation of dicentrics and monitor dicentric breakage in cells progressing synchronously through mitosis.

In progress (confidential)

In progress

Lopez V., Barinova N., Onishi M., Pobiega S., Pringle J., Dubrana K. and S. Marcand* (2015) Cytokinesis breaks dicentric chromosomes preferentially at pericentromeric regions and telomere fusions. Genes & Development 29:322-336.

Dicentric chromosomes are abnormal structures that are particularly challenging to genome stability. Dicentrics are products of erroneous DNA repair events (e.g. accidental telomere fusions, double-strand breaks-induced translocations). During mitosis, they form anaphase bridges when the two linked centromeres are pulled toward opposite spindle poles, resulting in breakage between the centromeres by an unknown mechanism. Newly broken ends cause cell death or are fused, creating further rearrangements. Its consequences for karyotype evolution and for gene deletions and amplifications through breakage-fusion-bridge cycles are well established but the underlying mechanisms remain for a large part unexplored.
The general aim of this project is to increase our knowledge on how a eukaryotic cell avoids and processes dicentric chromosomes. Using advanced yeast molecular genetics and cell biology approaches, we have developed highly sensitive and quantitative assays to detect the formation of dicentrics and monitor dicentric breakage in cells progressing synchronously through mitosis. We want to identify and dissect the pathways preventing dicentrics formation and decipher how dicentric are broken upon mitotic exit and cytokinesis.
Specifically, we will search for the determinants of dicentric occurrence in cycling versus quiescent cells and how they are impacted by nuclear organisation and endogenous and exogenous stresses, including double strand breaks. We will also address how specific mechanisms prevent telomere fusions by inhibiting the NHEJ double-strand break repair pathway at telomeres. We will determine the precise role of cytokinesis in dicentric breakage, whether a nuclease is directly involved and the mechanisms that favour breakage at specific hot spots (e.g. telomere fusions).
The output of this project will be new basic knowledge on how a eukaryotic cell avoids dicentric chromosomes and process them once they occur. In addition to a better understanding on how genomes are maintained and evolve, this new knowledge on dicentrics will be highly relevant to the fields of oncology, aging and radiobiology where dicentrics can be important contributors to pathological states.