Characterization of the bifunctional kinase/phosphatase PleC regulating cell cycle progression and development in Caulobacter crescentus

  • Thomas Brochier

Student thesis: Master typesMaster en biochimie et biologie moléculaire et cellulaire

Résumé

Asymmetric cell division is a strategy used by bacteria to produce a specialized offspring perfectly adapted to environmental conditions. Diversification provides an indisputable advantage to the whole population when living in challenging environments. The alphaproteobacterium Caulobacter crescentus became a model organism for studying of cell cycle regulation and development because it <livides asymmetrically to adopt a dimorphic life cycle composed of the motile - non-replicative - swarmer cell and the sessile stalked cell competent for replication. In addition, the entry of the swarmer cell into the cell cycle is concomitant with its differentiation into a stalked cell. C. crescentus cell cycle and development are regulated by a complex regulatory pathway, composed of multiple interconnected regulators belonging to the two-component signal transduction system (TCS). The major output of this regulatory pathway is the tight control of the master cell cycle regulator CtrA. Indeed, its activity is rigorously regulated to be optimal in the G 1/swarmer cells to inhibit initiation of DNA replication, and annihilated at the G 1-S transition to allow this process to happen. This dichotomy between high and low CtrA activity respectively in the swarmer and stalked cells relies on the bifunctional histidine kinase (HK) PleC, which harbors both kinase and phosphatase activities. Indeed, PleC works as a bistable switch by altemating its activity from phosphatase to kinase (P-K), tuming the activity of CtrA ON and OFF respectively. In this work, we first characterized catalytic mutants of PleC to evaluate the implication of each activity on the physiology of C. crescentus. In addition, we investigated the proteolytic degradation of PleC and tried to uncover actors responsible for its transient disappearance at the G 1-S transition of the cell cycle. Finally, we performed genome-wide approaches to identify potential new actors involved in the regulation of PleC and CtrA.
la date de réponse2018
langue originaleAnglais
L'institution diplômante
  • Universite de Namur
SuperviseurRegis Hallez (Promoteur)

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