title: Protective role of RAD50 on chromatin bridges during abnormal cytokinesis.
abstract: Faithful chromosome segregation is required for preserving genomic integrity. Failure of this process may entail chromatin bridges preventing normal cytokinesis. To test whether RAD50, a protein normally involved in DNA double-strand break repair, is involved in abnormal cytokinesis and formation of chromatin bridges, we used immunocytochemical and protein interaction assays. RAD50 localizes to chromatin bridges during aberrant cytokinesis and subsequent stages of the cell cycle, either decorating the entire bridge or focally accumulating at the midbody zone. Ionizing radiation led to an ∼4-fold increase in the rate of chromatin bridges in an ataxia telangiectatica mutated (ATM)-dependent manner in human RAD50-proficient fibroblasts but not in RAD50-deficient cells. Cells with a RAD50-positive chromatin bridge were able to continue cell cycling and to progress through S phase (44%), whereas RAD50 knockdown caused a deficiency in chromatin bridges as well as an ∼4-fold prolonged duration of mitosis. RAD50 colocalized and directly interacted with Aurora B kinase and phospho-histone H3, and Aurora B kinase inhibition led to a deficiency in RAD50-positive bridges. Based on these observations, we propose that RAD50 is a crucial factor for the stabilization and shielding of chromatin bridges. Our study provides evidence for a hitherto unknown role of RAD50 in abnormal cytokinesis.
authors.affiliation: 1Hannover Medical School, Gynaecology Research Unit (OE 6411), Carl-Neuberg-Str. 1, D-30625 Hannover, Germany. schroeder-heurich.bianca@mh-hannover.de.
authors.forename: Bianca
authors.initials: B
authors.lastname: Schröder-Heurich
authors.forename: Britta
authors.initials: B
authors.lastname: Wieland
authors.forename: Martin F
authors.initials: MF
authors.lastname: Lavin
authors.forename: Detlev
authors.initials: D
authors.lastname: Schindler
authors.forename: Thilo
authors.initials: T
authors.lastname: Dörk
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000502:physiology*; D017766:Acid Anhydride Hydrolases; D000818:Animals; D002461:Cell Line, Transformed; D002843:Chromatin / Q000502:physiology*; D048749:Cytokinesis; D004268:DNA-Binding Proteins; D051379:Mice; D041681:NIH 3T3 Cells
chemical_list: D018528:ATP-Binding Cassette Transporters; D002843:Chromatin; D004268:DNA-Binding Proteins; D017766:Acid Anhydride Hydrolases; C495198:Rad50 protein, mouse
keywords: Aurora B; DNA damage; MRN complex; anaphase bridges; mitosis