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  Director : Arcangioli Benoît (barcan@pasteur.fr)



Our work is aimed at understanding the process of asymmetric division in the fission yeast, S. pombe. This mechanism is novel and couples the processes of DNA replication and recombination. The conservation of these two fundamental pathways through evolution allows us to use this system as a model in the study of chromosome structure and stability in eucaryotes.



We are studying the molecular nature of a chromosomal epigenetic phenomena controlling the asymmetric division in the fission yeast, S. pombe. This process is responsible for mating-type switching in this yeast and allows one haploid cell type (male or female) to produce a cell population containing roughly the same proportion of the two cell types. This process is essential for correct progression of the life cycle, allowing sexual fusion to form diploid cells and sporulation to produce four new haploid cells.

Our previous studies have shown that this process is initiated by a single strand DNA modification at the mating-type locus and implicates the process of DNA replication. The DNA modification appears on only one of the two sister chromatids during DNA replication of the lagging strand, is maintained throughout the progression of the cell cycle and triggers mating-type switches during the next S-phase. The processes involved in the formation or the maintenance of this DNA modification is still unknown. However, we recently have shown that the DNA replication of the mating-type locus do not follow the classical semi-conservative mode of the DNA replication and providing strong molecular evidence which the asymmetric mating-type switching pattern.

Atanas Kaykov (PhD student), analyses the Cis-acting elements required for the formation and the maintenance of the DNA modification at the mating-type locus. Allyson Holmes (Postdoc), developed new tools to understand the role of some switching factors and the order of events required in this process.

Another aspect of our work is related to the function of the sap1 gene. Initially required for mating-type switching, Sap1 is also involved in an essential cellular function. Raynald de Lahondes (PhD student) found that Sap1 plays an important role in the cohesion/condensation process. This function might be required to maintain the DNA modification on one sister chromatid somehow excluding the repair machinery from the other intact sister during cell cycle progression. This part of the project is now conducted by Blerta Xhemalce (PhD student). The role of Sap1, a site specific DNA binding protein, in these processes may have an important impact in chromosomes organisation and dynamic.


puce Publications of the unit on Pasteur's references database


  Office staff Researchers Scientific trainees Other personnel

Lavenir, Armelle, alavenir@pasteur.fr (1/4 time)


Kaykov Atanas, Doctorant

Xhemalce Blerta, DEA

Holmes Allyson, Post-doctorante

Gilbert Michele, Technician

Legat Geneviève, Technician (1/2 time)


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