I2BC Paris-Saclay

Physical interaction and functional interplay between essential co-regulators in transcription and chromatin organization, Mediator and RSC chromatin remodeler, contributes to nucleosome-depleted region formation at promoters and +1 nucleosome positioning.

Eukaryotic DNA is compactly structured through chromatin organization which governs and influences all DNA transactions. Regulation of transcription is a key phenomenon of gene expression whose alterations lead to severe human pathologies. Multisubunit coregulator complexes can act on chromatin structure as chromatin modifiers or remodelers, or stimulate the assembly of the transcriptional machinery. Mediator is an essential and conserved coactivator thought to act in concert with chromatin regulators. However, it remains largely unknown how their functions are coordinated. The team of J. Soutourina (Genome biology/I2BC and Institute Joliot, CEA/CNRS/Paris-Saclay) provides evidence in the budding yeast that Mediator establishes physical contact with RSC (Remodels the Structure of Chromatin), a conserved and essential chromatin remodeling complex that is crucial for nucleosome-depleted region (NDR) formation. The role of Mediator-RSC interaction in their chromatin binding, nucleosome occupancy and transcription was determined on a genomic scale. Mediator and RSC co-localize on wide NDRs of promoter regions, and specific Mediator mutations affect nucleosome eviction and stability of +1 nucleosome associated with transcription-start site. This work shows that Mediator contributes to RSC remodeling function to shape NDRs and maintain chromatin organization on promoter regions. It will help in our understanding of transcriptional regulation in the chromatin context relevant for severe diseases.

More information: doi.org/10.1016/j.celrep.2023.112465 

Contact: Julie Soutourina <julie.soutourina@i2bc.paris-saclay.fr>

Registration open, here

High Throughput Screening Reveals genes involved in pre-symptomatic colonization of potato roots by a bacterial pathogen.

Dickeya and Pectobacterium species are necrotrophic pathogens that macerate stems (blackleg disease) and tubers (soft rot disease) of Solanum tuberosum. They proliferate by exploiting plant cell remains. They also colonize roots, even if no symptoms are observed. The genes involved in pre-symptomatic root colonization are poorly understood. Here, transposon-sequencing (Tn-seq) analysis of Dickeya solani living in macerated tissues revealed 126 genes important for competitive colonization of tuber lesions and 207 for stem lesions, including 96 genes common to both conditions. In root colonization, Tn-seq highlighted 83 genes, all different from those in stem and tuber lesion conditions. This work revealed novel traits and pathways important for understanding how the D. solani pathogen efficiently survives on roots, persists in the environment, and colonizes progeny tubers.

More information: https://doi.org/10.3389/fpls.2023.1154110

Contact: Denis Faure <denis.faure@i2bc.paris-saclay.fr>