Organisation génomique de l’activité transcriptionnelle du récepteur aux oestrogènes – GORGONES

A major breakthrough in research on eukaryotic transcription is the recent recognition that cell-specific transcription programs utilize, in addition to genetic information, nuclear components originally thought to be mere 'architectural' material with poor regulatory contribution. Dynamic engagements of given protein complexes, histones and chromatin modifications, as well as DNA methylation assume indeed important regulatory roles in transcription. This additional level of regulatory information beyond the linear DNA sequence is the epigenome, and can be considered as a three-dimensional framework that specifies and organizes the expression of the genome. The spatio-temporal coordination of gene transcription is orchestrated by transient bindings of transcription factors, inducing in turn a cascade of enzymatic reactions via an ordered recruitment of various cofactors that modulate epigenome marks. This is exemplified by the combinatorial and cyclical recruitment of proteins on promoters regulated by the estrogen receptor (ER). Promoter-specific variations in the temporal recruitment of ER diverse cofactors during gene transcriptional activation are important parameters for introducing variations in gene response to estradiol (E2). However, the mechanisms underlying these processes are still poorly understood, notably those considering the interplays between chromatin organization, epigenome and cofactors recruitment. Within this context, our main objective is to elucidate mechanisms that govern chromatin dynamics during transcriptional regulation. This will be addressed within the context of isolated E2-regulated genes but also in the case of clustered co-regulated genes. In combinations with other methods, kinetic Chromatin ImmunoPrecipitation (ChIP) experiments will generate data to correlate promoter structure and organization (cis elements, chromatin structure, inclusion within gene clusters') to the specific patterns of cofactors recruitment. Planned experiments will (i) provide information on promoter-specific mechanisms engaged by ER when regulating transcription; (ii) consider individual and clustered target genes chromatin structure in correlation with these activities.