Analyse génomique et génétique du programme de réplication chez l'humain – Genomrep

In order to maintain genome integrity, DNA replication has the difficult task to insure that each time a cell divide, the genome is duplicated exactly once per cell cycle. Although many known checkpoints control replication elongation, evidence suggests that there are several different mechanisms by which inappropriate replication start sites usage can give rise to genomic instability and cancer. In metazoa, DNA replication starts from thousands of chromosomal sites, termed replication origins. A spatio-temporal program controls the location and the moment when origins fire during S phase. Mechanisms that regulate this program are still poorly understood. However so far less than 30 origins have been identified in human cells and no consensus sequence could be found from this weak information. Our laboratory develops genome-wide studies aimed at getting more insights into this regulation. We have recently established a new genome-wide mapping of replication origins along 1% of the genome based on chip approaches in Hela cells. Our study identifies 283 origins increasing by an order of magnitude the number of currently known replication origins. This study suggests a strong connection between replication origins and transcription regulatory elements. In this new project, we propose to develop bioinformatics studies in order to identify cis-regulatory elements. We will also extend our mapping to the whole human genome by using new high throughput techniques of sequencing. This approach will allow us to validate models proposed by our first set of origins. We will also analyze the pattern of initiation in Stem cells in order to test whether this program is significantly modulated in pluripotent cells. We also propose to make genome-wide studies of the temporal program of replication in order to find how origin firing is regulated during S phase. Finally, the chicken DT40 genetic tool will be used for testing and validating hypotheses drawn by our genome wide studies.