The ClpPX protease is required for radioresistance and regulates cell division after γ‐irradiation in <i>Deinococcus radiodurans</i>

Abstract

Protein degradation in bacteria is involved in diverse cellular responses to environmental stimuli and in removing potentially toxic damaged proteins or protein aggregates. ATP-dependent proteases play a key role in these processes. Here, we have individually inactivated all the ATP-dependent proteases belonging to the Clp or Lon families in Deinococcus radiodurans. The mutants were tested for survival after gamma-irradiation and for sensitivity to the tRNA analogue puromycin in order to assess the impact of each disruption on radioresistance, as well as on proteolysis of misfolded proteins. We found that inactivation of the ClpPX protease significantly decreased cell survival at elevated gamma-irradiation doses, while inactivation of Lon1 and Lon2 proteases reduced resistance to puromycin, suggesting that they play a role in eliminating damaged proteins. Mutants devoid of ClpPX protease displayed altered kinetics of DNA double-strand break repair and resumed cell division after an exceedingly long lag phase following completion of DNA repair. During this stasis period, most of the DeltaclpPX irradiated cells showed decondensed nucleoids and abnormal septa and some cells were devoid of DNA. We propose that the ClpPX protease is involved in the control of proper chromosome segregation and cell division in cells recovering from DNA damage.