Redox signaling through zinc activates the radiation response in Deinococcus bacteria

Romaric Magerand,Laurence Blanchard,Arjan De Groot,Pascal Rey

doi:10.1038/s41598-021-84026-x

Abstract

Deinococcus bacteria are extremely resistant to radiation and other DNA damage- and oxidative stress-generating conditions. An efficient SOS-independent response mechanism inducing expression of several DNA repair genes is essential for this resistance, and is controlled by metalloprotease IrrE that cleaves and inactivates transcriptional repressor DdrO. Here, we identify the molecular signaling mechanism that triggers DdrO cleavage. We show that reactive oxygen species (ROS) stimulate the zinc-dependent metalloprotease activity of IrrE in Deinococcus. Sudden exposure of Deinococcus to zinc excess also rapidly induces DdrO cleavage, but is not accompanied by ROS production and DNA damage. Further, oxidative treatment leads to an increase of intracellular free zinc, indicating that IrrE activity is very likely stimulated directly by elevated levels of available zinc ions. We conclude that radiation and oxidative stress induce changes in redox homeostasis that result in IrrE activation by zinc in Deinococcus. We propose that a part of the zinc pool coordinated with cysteine thiolates is released due to their oxidation. Predicted regulation systems involving IrrE- and DdrO-like proteins are present in many bacteria, including pathogens, suggesting that such a redox signaling pathway including zinc as a second messenger is widespread and participates in various stress responses.

Highlights

Deinococcus bacteria are extremely resistant to radiation and other DNA damage- and oxidative stress-generating conditions
TEMPOL, which catalyzes superoxide dismutation, facilitates catalase-like metabolism of H2O2 and limits hydroxyl radical formation[41,42,43], inhibited DdrO cleavage in cells exposed to mitomycin C (MMC) (Fig. 1)
When the cells were directly exposed to H2O2 for 10 min, DdrO cleavage was efficiently induced, which was inhibited by thiourea and TEMPOL (Fig. 1), further confirming the participation of redox signaling in IrrE activation

Summary

Introduction

Deinococcus bacteria are extremely resistant to radiation and other DNA damage- and oxidative stress-generating conditions. An efficient SOS-independent response mechanism inducing expression of several DNA repair genes is essential for this resistance, and is controlled by metalloprotease IrrE that cleaves and inactivates transcriptional repressor DdrO. In case of DNA damage-generating stress, many bacteria use the SOS response to induce expression of DNA repair genes. In Deinococcus bacteria, induction of recA and other DNA repair genes occurs in a RecA/LexA-independent manner and in the present work we aim to identify the intracellular molecular signal that induces this SOSindependent response. Deinococcus species are famous for their extreme tolerance to DNA damage- and oxidative stress-generating conditions such as radiation and desiccation, and for their capacity to repair massive DNA damage[3,4,5,6]. Predicted but largely uncharacterized COG2856/XRE protein pairs have been identified in many other bacterial genera, including pathogens and bacteria used in biotechnological industry[14,19,27,28,29], suggesting that stress response mechanisms involving such protein pairs are more widespread than currently recognized

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