Prepared in INSERM U823, Institut Albert Bonniot, Grenoble, France; under the direction of Stefan Dimitrov, head of the “Chromatin and Epigenetic” group. Publicly defended on December 16th, 2011 at the Faculté de Médecine et de Pharmacie de Grenoble.

Abstract

The histone variant CENP-A is the epigenetic factor responsible for centromere determination. It allows the recruitment of a handful of centromeric proteins, and thus acts as the primary foundation for the kinetochore. It comprises an unstructured NH₂-terminal domain to which no precise function has been assigned yet, although it is established that the mere presence of that domain is required for proper centromere function and thus successful completion of mitosis. We have established several cell lines stably expressing GFP-tagged CENP-A constructs, allowing us to perform pseudogenetic experiments by siRNA-mediated silencing of the endogenous CENP-A. Our results show a dramatic increase of mitotic defects and plurinuclear cells when cells express only the globular domain of CENP-A; this is in accordance with the litterature and confirms the importance of the NH₂-terminal tail. More importantly, a similar increase of mitotic defects is observed when cells express a full-length, but non-phosphatable, CENP-A. Our results show the involvement of the phosphatable serine 7 of CENP-A in the successful completion of mitosis, and may suggest that the role of the whole NH₂-terminal tail of CENP-A could be reduced to this single phosphorylation event.

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Presentation

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The poster I presented at the EMBO Meeting, september 2011, in Vienna: