Protein scaffold interaction12/13/2022 ![]() Here we characterize the physical interactions between PopZ and PodJ within the new cell pole microdomain, and we demonstrate that PodJ-PopZ interaction coordinates the signaling transductions between their respective clients to ensure reliable asymmetric cell division. Therefore, these previous studies suggest that similar to that of PopZ and SpmX at the old cell pole 2, there are functional interactions between the PopZ and PodJ scaffolds at the opposite cell pole. Downstream, this resulted in the down-regulation of the CtrA signaling pathway 21, 22 and reduced levels of the CtrA-regulated gene PilA 19, 21, 22. Moreover, Δ podJ strains exhibited moderate loss of the localization of PopZ’s client proteins at the new cell pole 21. Deletion of the PodJ scaffold results in failure to recruit PleC histidine kinase to the new cell pole 19, 20 and less monopolar accumulation of DivL at the new cell pole 21. SpmX bridges the interaction between PopZ and DivJ, and can even nucleate the formation of new PopZ microdomains at ectopic poles upon overexpression 2.Īt the new cell pole, the scaffold proteins PopZ and PodJ play roles in polar assembly. On the other hand, the histidine kinase DivJ specifically resides at the old cell pole, and the scaffolding protein SpmX mediates this specific recruitment. PopZ also serves as an attachment site for the ParB- parS centromere during chromosome segregation 15, 18. The PopZ scaffold promotes bipolar accumulation of the histidine kinase CckA and its modulator DivL 16. The new and old cell pole signaling hubs share some common clients, while others are selectively recruited to each signaling hub. ![]() However, the mechanisms that enable a common scaffold to promote the formation of two compositionally distinct biomolecular condensates remains unclear. coli reconstitution strategies 2, 16, 17 have shown that PopZ dynamically recruits multiple distinct protein clients at each cell poles in pre-divisional cells 18. Single-molecule tracking experiments 13, FLIP studies 16, and E. PopZ self-assembles as a micron-sized biomolecular condensate at each cell pole 13, 15, 16. A scaffolding factor that is required for cell polarity is the protein PopZ. Consequently, not only temporal 12 but also spatial 13 regulation of CtrA phosphorylation coordinate transcription of more than 90 developmental genes 14. This intricate subcellular organization of CtrA regulators leads to selective CtrA phosphorylation at the new swarmer pole and dephosphorylation CtrA at the old stalked cell pole ( Figure 1) 6, 11. crescentus cells.Īmongst the client proteins asymmetrically polarized are a set of two-component signaling systems that collectively regulate the master regulator CtrA 3, 6- 10. Therefore, segregation of PopZ protein at the old pole and recruitment of newly translated PopZ at the new pole via the PodJ scaffold ensures stringent inheritance and maintenance of the polarity axis within dividing C. Additionally, this PopZ-PodJ interaction is crucial for anchoring PodJ and preventing PodJ extracellular loss at the old cell pole through unknown mechanism. Elimination of the PodJ-PopZ interaction impacts PopZ client proteins, leading to chromosome segregation defects in one-third of cells. Our studies suggest that interactions between PodJ and PopZ promotes the sequestration of older PopZ and robust accumulation of newl PopZ at the new cell pole. Time-course imaging of a mCherry-sfGFP-PopZ fluorescent timer throughout the cell cycle revealed that existing PopZ resides at the old cell pole while newly translated PopZ accumulates at the new cell pole. ![]() Here we identify an interaction between the scaffolds PodJ and PopZ that regulates the assembly of the new cell pole signaling complex. The localization of two biochemically distinct signaling hubs at opposite cell poles provides the foundation for asymmetric cell division in Caulobacter crescentus. ![]()
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