Phosphorylation of FtsZ and FtsA by a DNA Damage-Responsive Ser/Thr Protein Kinase Affects Their Functional Interactions in Deinococcus radiodurans.

Ganesh K Maurya,Kruti Modi,Hari S Misra,Yogendra S Rajpurohit,Manisha Banerjee,Reema Chaudhary,Craig D Ellermeier

doi:10.1128/msphere.00325-18

Ganesh K Maurya, Kruti Modi + Show 5 more

Open Access

https://doi.org/10.1128/msphere.00325-18

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Abstract

Deinococcus radiodurans, a highly radioresistant bacterium, does not show LexA-dependent regulation of recA expression in response to DNA damage. On the other hand, phosphorylation of DNA repair proteins such as PprA and RecA by a DNA damage-responsive Ser/Thr protein kinase (STPK) (RqkA) could improve their DNA metabolic activities as well as their roles in the radioresistance of D.radiodurans Here we report RqkA-mediated phosphorylation of cell division proteins FtsZ and FtsA in vitro and in surrogate Escherichia coli bacteria expressing RqkA. Mass spectrometric analysis mapped serine 235 and serine 335 in FtsZ and threonine 272, serine 370, and serine 386 in FtsA as potential phosphorylation sites. Although the levels of FtsZ did not change during postirradiation recovery (PIR), phosphorylation of both FtsZ and FtsA showed a kinetic change during PIR. However, in an rqkA mutant of D.radiodurans, though FtsZ underwent phosphorylation, no kinetic change in phosphorylation was observed. Further, RqkA adversely affected FtsA interaction with FtsZ, and phosphorylated FtsZ showed higher GTPase activity than unphosphorylated FtsZ. These results suggest that both FtsZ and FtsA are phosphoproteins in D.radiodurans The increased phosphorylation of FtsZ in response to radiation damage in the wild-type strain but not in an rqkA mutant seems to be regulating the functional interaction of FtsZ with FtsA. For the first time, we demonstrate the role of a DNA damage-responsive STPK (RqkA) in the regulation of functional interaction of cell division proteins in this bacterium.IMPORTANCE The LexA/RecA-type SOS response is the only characterized mechanism of DNA damage response in bacteria. It regulates cell cycle by attenuating the functions of cell division protein FtsZ and inducing the expression of DNA repair proteins. There are bacteria, including Deinococcus radiodurans, that do not show this classical SOS response. D.radiodurans is known for its extraordinary resistance to gamma radiation, and a DNA damage-responsive Ser/Thr protein kinase (RqkA) has been characterized for its role in radioresistance. RqkA phosphorylates a large number of proteins in solution. The phosphorylation of RecA and PprA by RqkA enhanced their activities. FtsZ phosphorylation is inducible by gamma radiation in wild-type D.radiodurans but not in an rqkA mutant. Phosphorylation affected the interaction of FtsZ and FtsA in this bacterium. This study, therefore, brought forth some findings that might lead to the discovery of a new mechanism regulating the bacterial cell cycle in response to DNA damage.

Highlights

Deinococcus radiodurans, a highly radioresistant bacterium, does not show LexA-dependent regulation of recA expression in response to DNA damage
Tion status of FtsZ and FtsA when present together was monitored in surrogate E. coli cells expressing RqkA of D. radiodurans
Unlike the results seen with the wild type (Fig. 2D), the ratio of FtsZ interacting phosphoprotein (FIPP) (P-FtsA) to P-FtsZ did not change during postirradiation recovery (PIR) in the rqkA mutant (Fig. 5F). These results clearly suggested that FtsZ becomes phosphorylated in this bacterium, the ¥ radiation stimulation of FtsZ phosphorylation seems to be contributed by RqkA, which is characterized as a DNA damage-responsive Ser/Thr protein kinase in this bacterium

Summary

Introduction

Deinococcus radiodurans, a highly radioresistant bacterium, does not show LexA-dependent regulation of recA expression in response to DNA damage. We demonstrate the role of a DNA damage-responsive STPK (RqkA) in the regulation of functional interaction of cell division proteins in this bacterium. IMPORTANCE The LexA/RecA-type SOS response is the only characterized mechanism of DNA damage response in bacteria It regulates cell cycle by attenuating the functions of cell division protein FtsZ and inducing the expression of DNA repair proteins. The phosphorylation of DNA repair proteins such as RecA and PprA (a pleiotropic protein involved in DNA repair in Deinococcus) by RqkA and the subsequent improvement in their role(s) in the radioresistance of this bacterium have been demonstrated [28, 29] Cell division proteins such as FtsZ and FtsA of D. radiodurans are 35% and 46% identical to homologues in E. coli, respectively. The molecular mechanism(s) regulating cell cycle arrest and FtsZ function in response to ␥-radiation damage would be worth understanding in this msphere.asm.org 2

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