FtsZ phosphorylation brings about growth arrest upon DNA damage in Deinococcus radiodurans

Abstract

The polymerization/depolymerization dynamics of FtsZ plays the pivotal role in cell division in majority bacteria. Deinococcus radiodurans, a radiation resistant bacterium, shows an arrest of growth in response to DNA damage, despite no change in the level of FtsZ. This bacterium does not deploy LexA/RecA type of DNA damage response and cell cycle regulation, and its genome does not encode homologs of E. colis SulA, which attenuate FtsZ functions in response to DNA damage in different bacteria. A radiation responsive Ser/Thr quinoprotein kinase (RqkA) characterized for its role in radiation resistance in this bacterium, could phosphorylate several cognate proteins including FtsZ (drFtsZ) at Serine 235 (S235) and Serine 335 (S335) residues. Here, we report the detailed characterization of S235 and S335 phosphorylation effect in the regulation of drFtsZ functions, and demonstrated that the phospho-mimetic replacements of these residues in drFtsZ had grossly affected its functions that could result in cell cycle arrest in response to DNA damage in D. radiodurans. Interestingly, the phospho-ablative replacements were found to be nearly similar to drFtsZ while phospho-mimetic mutant showed the loss of signatures characteristics to wild type enzyme including the arrest in its dynamics under normal conditions. The post-bleaching recovery kinetics for drFtsZ and phospho-mimetic mutant was nearly similar at 2h post irradiation recovery but found to be different under normal conditions. These results highlighted the role of S/T phosphorylation in the regulation of drFtsZ functions and cell cycle arrest in response to DNA damage and is first time demonstrated in this prokaryote.