Ion Beams from Physics to Therapy

Sunday, October 16, 2005 10:15 AM-12:00 PM Room No. 610/612
Chair(s): Kronenberg, Amy

(SY013) Dynamics of repair-protein localization to particle tracks.

Taucher-Scholz, Gisela*,1, 1 Biopysics, Darmstadt, Hessen, Germany

ABSTRACT- The biological effects of charged particle radiation are based on physical parameters like the extremely localized microscopic pattern of dose deposition, which can be visualized in the form of radiation-induced foci at the sites of particle traversal using immunocytochemical detection or GFP-tagged DNA repair proteins. The spatial distribution of proteins can also be analyzed along the ion trajectories using a geometry characterized by a small angle between the incident beam and the monolayer of cells. Similar patterns of protein aggregates obtained for functionally different proteins irrespective of the type of ion beam applied, suggest that not the pattern of dose deposition but the underlying chromatin structure determines the distribution of protein clusters along tracks. However, changes in track morphology with time and a constricted migration of foci can be observed, probably in connection with lesion processing. To study the spatio-temporal dynamics of repair-related proteins we developed a remote-controlled microscopic system directly at the beamline, capable of analyzing early responses during irradiation with heavy ions in living cells. Time-lapse images of GFP-coupled DNA repair proteins revealed accumulations within seconds at sites of ion traversals indicating a very fast recruitment to damaged sites. Using the beamline microscope and scratch replication labeling or solid state track detection we also showed that repair-protein localization to tracks is not connected to a large scale chromatin movement at early times after irradiation. The results demonstrate that locally restricted lesions generated by ion tracks offer a tool to elucidate the spatio-temporal dynamics of proteins involved in the DNA-damage response after ionizing irradiation.

Key words: heavy ion, tracks, foci, chromatin

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2005 RRS