MazEF Toxin-Antitoxin System-Mediated DNA Damage Stress Response in Deinococcus radiodurans

Abstract

<i>Deinococcus radiodurans</i> shows marked resistance to various types of DNA-damaging agents, including mitomycin C (MMC). A type II toxin-antitoxin (TA) system that responds to DNA damage stress was identified in <i>D. radiodurans</i>, comprising the toxin MazF-dr and the antitoxin MazE-dr. The cleavage specificity of MazF-dr, an endoribonuclease, was previously characterized. Here, we further investigated the regulatory role of the MazEF system in the response to DNA damage stress in <i>D. radiodurans</i>. The crystal structure of <i>D. radiodurans</i> MazF (MazF-dr) was determined at a resolution of 1.3 Å and is the first structure of the toxin of the TA system of <i>D. radiodurans</i>. MazF-dr forms a dimer mediated by the presence of interlocked loops. Transcriptional analysis revealed 650 downregulated genes in the wild-type (WT) strain, but not in the <i>mazEF</i> mutant strain, which are potentially regulated by MazEF-dr in response to MMC treatment. Some of these genes are involved in membrane trafficking and metal ion transportation. Subsequently, compared with the WT strain, the <i>mazEF</i> mutant strain exhibited much lower MMC-induced intracellular iron concentrations, reactive oxygen species (ROS), and protein carbonylation levels. These results provide evidence that MazEF-mediated cell death in <i>D. radiodurans</i> might be caused by an increase in ROS accumulation upon DNA damage stress.