Molecular and cellular caracterization of novel bacterial nucleomodulins – NucPath

To achieve this we will identify their eukaryotic targets and determine their mode of action in parallel with structure-function studies to define key functional domains involved in the nuclear-modulatory properties of these effectors. In addition, we will analyse their impact on host chromatin and gene expression, which may be contributing to modulation of cellular responses, essential for onset of a chronic infection.

We have identified the cellular targets of two of these nucleomodulins and have shown they are required for successful infection. We have also solved the structure and defined the key aminoacids implicated in these interactions. We are currently studying the molecular pathways implicated during infection. As our results have not yet been published we cannot share the information with the general public at this stage.

Extremely exciting results have been obtained implicating a novel pathway in bacterial pathogenesis. We will continue to investigate this further in the next two years.

ongoing

Bacterial targeting of the nucleus of host cells during infection is an important virulence strategy shared by growing number bacterial pathogens. We have recently identified four novel nucleomodulins, effectors targeting the nucleus of host cells, including BnpA that localizes to specific nuclear bodies where it can modulate sub-nuclear spatial dynamics. These novel Brucella effectors show no homology to previously studied bacterial nucleomodulins and therefore may provide insight into nuclear processes and the function of nuclear bodies, central in cell biology. The goal of NucPath is to characterize these nucleomodulins by defining how they alter nuclear dynamics and affect host gene expression, allowing Brucella to subvert host responses and establish an intracellular niche suitable for replication. To achieve this we will identify their eukaryotic targets and determine their mode of action in parallel with structure-function studies to define key functional domains involved in the nuclear-modulatory properties of these effectors. In addition, we will analyse their impact on host chromatin and gene expression, which may be contributing to modulation of cellular responses, essential for onset of a chronic infection. We will investigate their mode of secretion and translocation into host cells, which surprisingly seems independent of the type IV secretion system described for Brucella. Finally, this work will be put into context of animal and human isolates of different Brucella species by determining sequence and expression variability of the different genes encoding Brucella nucleomodulins.

Overall, this ambitious research program is on the forefront of an important emerging topic in bacterial pathogenesis, with the originality of combining molecular and structural studies with advanced cellular imaging to characterize the mode of action of bacterial nucleomodulins. To support this Young Researcher ANR grant request, in the past two years I established my independent research team, assembled extensive preliminary data that is presented within the scientific proposal and developed a solid network of collaborations that will ensure we achieve the proposed objectives. This project will not only reveal how novel Brucella effectors might modulate host functions and generate knowledge on mechanisms of virulence common to many plant and human pathogens, but may also give new insight into the functioning of the cellular machinery controlling nuclear dynamics which is often perturbed in human disease states like inflammatory diseases and cancer.