title: Recruitment kinetics of DNA repair proteins Mdc1 and Rad52 but not 53BP1 depend on damage complexity.
abstract: The recruitment kinetics of double-strand break (DSB) signaling and repair proteins Mdc1, 53BP1 and Rad52 into radiation-induced foci was studied by live-cell fluorescence microscopy after ion microirradiation. To investigate the influence of damage density and complexity on recruitment kinetics, which cannot be done by UV laser irradiation used in former studies, we utilized 43 MeV carbon ions with high linear energy transfer per ion (LET = 370 keV/µm) to create a large fraction of clustered DSBs, thus forming complex DNA damage, and 20 MeV protons with low LET (LET = 2.6 keV/µm) to create mainly isolated DSBs. Kinetics for all three proteins was characterized by a time lag period T(0) after irradiation, during which no foci are formed. Subsequently, the proteins accumulate into foci with characteristic mean recruitment times τ(1). Mdc1 accumulates faster (T(0) = 17 ± 2 s, τ(1) = 98 ± 11 s) than 53BP1 (T(0) = 77 ± 7 s, τ(1) = 310 ± 60 s) after high LET irradiation. However, recruitment of Mdc1 slows down (T(0) = 73 ± 16 s, τ(1) = 1050 ± 270 s) after low LET irradiation. The recruitment kinetics of Rad52 is slower than that of Mdc1, but exhibits the same dependence on LET. In contrast, the mean recruitment time τ(1) of 53BP1 remains almost constant when varying LET. Comparison to literature data on Mdc1 recruitment after UV laser irradiation shows that this rather resembles recruitment after high than low LET ionizing radiation. So this work shows that damage quality has a large influence on repair processes and has to be considered when comparing different studies.
authors.affiliation: Angewandte Physik und Messtechnik LRT2, UniBw-München, Neubiberg, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Hable
authors.forename: Guido A
authors.initials: GA
authors.lastname: Drexler
authors.forename: Tino
authors.initials: T
authors.lastname: Brüning
authors.forename: Christian
authors.initials: C
authors.lastname: Burgdorf
authors.forename: Christoph
authors.initials: C
authors.lastname: Greubel
authors.forename: Anja
authors.initials: A
authors.lastname: Derer
authors.forename: Judith
authors.initials: J
authors.lastname: Seel
authors.forename: Hilmar
authors.initials: H
authors.lastname: Strickfaden
authors.forename: Thomas
authors.initials: T
authors.lastname: Cremer
authors.forename: Anna A
authors.initials: AA
authors.lastname: Friedl
authors.forename: Günther
authors.initials: G
authors.lastname: Dollinger
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D004249:DNA Damage; D004260:DNA Repair; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D007700:Kinetics; D009687:Nuclear Proteins / Q000378:metabolism*; D051721:Rad52 DNA Repair and Recombination Protein / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D000071857:Tumor Suppressor p53-Binding Protein 1; D014466:Ultraviolet Rays
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; C413163:MDC1 protein, human; D009687:Nuclear Proteins; C497194:RAD52 protein, human; D051721:Rad52 DNA Repair and Recombination Protein; C498301:TP53BP1 protein, human; D015534:Trans-Activators; D000071857:Tumor Suppressor p53-Binding Protein 1