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Updated: Feb 26, 2026

Laser Microirradiation to Study In Vivo Cellular Responses to Simple and Complex DNA Damage
Published on: January 31, 2018
Poly(ADP-Ribose)-Dependent Chromatin Remodeling in DNA Repair
Théo Lebeaupin1,2, Rebecca Smith1, Sébastien Huet2
1Department of Physiological Chemistry, Biomedical Center Munich, Ludwig-Maximilians-Universität München, Großhaderner Str. 9, 82152 Planegg-, Martinsried, Germany.
None:
The tightly packed and dynamic structure of chromatin can undergo major reorganization in response to endogenous or exogenous stimuli, such as the regulation of transcription or the cell cycle, or following DNA damage. A fast and local chromatin decondensation is observed upon DNA damage induced by laser micro-irradiation. This decondensation is under the control of poly(ADP-ribosyl)ation (PARylation) by PARP1, one of the first proteins recruited at the DNA damage sites. This chapter provides a step-by-step guide to perform and analyze chromatin decondensation upon DNA damage induction. The protocol is based on fluorescence microscopy of live cells expressing a core histone tagged with a photoactivatable fluorophore. Laser micro-irradiation is used to simultaneously induce DNA damage and activate the fluorescence signal within the irradiated area. This photo-perturbation experiment can be easily implemented on any confocal laser-scanning microscope equipped with a photoperturbation module. The experimental framework can also be used to follow chromatin relaxation in parallel with the recruitment kinetics of a protein of interest at DNA lesions in cells co-expressing the tagged histones and a second protein of interest fused to a different fluorescent tag.
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