title: Mre11-Rad50-Nbs1 complex is activated by hypertonicity.
abstract: When exposed to hypertonic conditions, cells accumulate double-strand DNA breaks (DSBs) like they are exposed to ionizing radiation. It has been proposed that inactivation of the Mre11-Rad50-Nbs1 (MRN) complex due to nuclear exit is responsible for the accumulation of DSBs as cells fail to repair DSBs produced during normal cellular activity. In this study, we examined the MRN complex in cells switched to hypertonicity. Surprisingly, we found that the MRN complex stayed in the nucleus and remained intact in response to hypertonicity. In fact, the MRN complex was dramatically activated after 4 h of switch to hypertonicity in a dose-dependent manner as shown by formation of foci. Activation of ATM and the MRN complex by hypertonicity and bleomycin was additive as was activation of their downstream targets including gammaH2AX and Chk2 indicating that the cellular response to DSB was intact in hypertonic conditions. Activation of Chk2 in response to hypertonicity was not observed in mutant cells with functionally impaired MRN complex confirming that they are in the same pathway. After 20 h of a switch to hypertonicity, MRN foci and gammaH2AX returned to a control level, suggesting that cells adapted to hypertonicity by repairing DNA. We conclude that cells respond normally to DSB and repair the DNA damages induced by hypertonicity.
authors.affiliation: Division of Nephrology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Mee Rie
authors.initials: MR
authors.lastname: Sheen
authors.forename: Seung Whan
authors.initials: SW
authors.lastname: Kim
authors.forename: Ju-Young
authors.initials: JY
authors.lastname: Jung
authors.forename: Joon Young
authors.initials: JY
authors.lastname: Ahn
authors.forename: Juong G
authors.initials: JG
authors.lastname: Rhee
authors.forename: H Moo
authors.initials: HM
authors.lastname: Kwon
authors.forename: Seung Kyoon
authors.initials: SK
authors.lastname: Woo
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D017766:Acid Anhydride Hydrolases; D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000378:metabolism; D064447:Checkpoint Kinase 2; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D000076228:MRE11 Homologue Protein; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D009997:Osmotic Pressure; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D017766:Acid Anhydride Hydrolases; D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins; D006657:Histones; D000076228:MRE11 Homologue Protein; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D012462:Saline Solution, Hypertonic; C121766:MRE11 protein, human; C512689:Mre11a protein, mouse; C112156:NBN protein, human; C466108:Nijmegen breakage syndrome 1 protein, mouse; C578634:CHEK2 protein, human; C578633:Chek2 protein, mouse; C112158:RAD50 protein, human; C495198:Rad50 protein, mouse; C475961:gamma-H2AX protein, mouse