Regulation of Bacterial Cell Cycle Progression by Redundant Phosphatases

Coppine, Jérôme and Kaczmarczyk, Andreas and Petit, Kenny and Brochier, Thomas and Jenal, Urs and Hallez, Régis. (2020) Regulation of Bacterial Cell Cycle Progression by Redundant Phosphatases. Journal of Bacteriology, 202 (17). e00345-20.

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Official URL: https://edoc.unibas.ch/79353/

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In the model organism; Caulobacter crescentus; , a network of two-component systems involving the response regulators CtrA, DivK, and PleD coordinates cell cycle progression with differentiation. Active phosphorylated CtrA prevents chromosome replication in G; 1; cells while simultaneously regulating expression of genes required for morphogenesis and development. At the G; 1; -S transition, phosphorylated DivK (DivK∼P) and PleD (PleD∼P) accumulate to indirectly inactivate CtrA, which triggers DNA replication initiation and concomitant cellular differentiation. The phosphatase PleC plays a pivotal role in this developmental program by keeping DivK and PleD phosphorylation levels low during G; 1; , thereby preventing premature CtrA inactivation. Here, we describe CckN as a second phosphatase akin to PleC that dephosphorylates DivK∼P and PleD∼P in G; 1; cells. However, in contrast to PleC, no kinase activity was detected with CckN. The effects of CckN inactivation are largely masked by PleC but become evident when PleC and DivJ, the major kinase for DivK and PleD, are absent. Accordingly, mild overexpression of; cckN; restores most phenotypic defects of a; pleC; null mutant. We also show that CckN and PleC are proteolytically degraded in a ClpXP-dependent way before the onset of the S phase. Surprisingly, known ClpX adaptors are dispensable for PleC and CckN proteolysis, raising the possibility that as yet unidentified proteolytic adaptors are required for the degradation of both phosphatases. Since; cckN; expression is induced in stationary phase, depending on the stress alarmone (p)ppGpp, we propose that CckN acts as an auxiliary factor responding to environmental stimuli to modulate CtrA activity under suboptimal conditions.; IMPORTANCE; Two-component signal transduction systems are widely used by bacteria to adequately respond to environmental changes by adjusting cellular parameters, including the cell cycle. In; Caulobacter crescentus; , PleC acts as a phosphatase that indirectly protects the response regulator CtrA from premature inactivation during the G; 1; phase of the cell cycle. Here, we provide genetic and biochemical evidence that PleC is seconded by another phosphatase, CckN. The activity of PleC and CckN phosphatases is restricted to the G; 1; phase since both proteins are degraded by ClpXP protease before the G; 1; -S transition. Degradation is independent of any known proteolytic adaptors and relies, in the case of CckN, on an unsuspected N-terminal degron. Our work illustrates a typical example of redundant functions between two-component proteins.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Growth & Development
05 Faculty of Science > Departement Biozentrum > Infection Biology > Molecular Microbiology (Jenal)
05 Faculty of Science > Departement Biozentrum > Growth & Development > Molecular Microbiology (Jenal)
05 Faculty of Science > Departement Biozentrum > Infection Biology
UniBasel Contributors:Jenal, Urs and Kaczmarczyk, Andreas
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Society for Microbiology
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:10 Feb 2021 02:30
Deposited On:24 Nov 2020 13:25

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