A large number of DNA damage response proteins accumulate at the damage sites after DNA is damaged,forming repair foci which can be observed by fluorescence microscope after Immunofluorescence staining[1].With the discovery of more and more DNA repair factors,there is also a question of how DNA damage response proteins migrate to the right place at the right time.According to their dynamics,DNA damage response proteins are divided into fast-recruiting proteins and slow-recruiting proteins[2].This classification can help us to establish the hierarchical organization of DNA damage identification and subsequent repair events.Fast recruitment proteins,such as XRCC1,reach their maximum within 12 min and then begin to dissociate rapidly from the site of injury[3].Their recruitment dynamics cannot be easily observed under the fixed cells,and can only be studied by live cell imaging Heavy ion microbeam irradiation can induce DNA damage in the submicron region of the nucleus and it is a very valuable technology to study the recruitment or modification of various factors of DNA damage in vivo.The intensive damage caused by heavy ions can be easily distinguished from spontaneous damage.It is especially suitable to observe the repair dynamics of proteins that do not form obvious repair foci through sparse ionizing radiation.
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