Quantification Of The Dynamics Of Dna Repair To Ionizing Radiation Via Colocalization Of 53bp1 And Gamma H2ax

Cellular response to stress can be manifested and visualized by measuring induced DNA damage. However, cellular systems can repair the damage through a variety of DNA repair pathways. It is important to characterize the dynamics of DNA repair in a variety of model systems. Such a characterization is another example of the video bioinformatics through harvesting and fixing of a large sample size at different time points. This chapter provides background and motivation for quantifying the dynamics of DNA damage induction and repair in cycling and stationary cells. These model systems indicate that the repair kinetics have a similar profile for gamma radiation; however, following iron ion exposure residual unrepaired damage is noted at longer times when assayed in stationary cells. Repair kinetics are visualized by immunofluorescence staining of phosphorylated histone gamma-H2AX and the DNA repair protein 53BP1. The kinetics are then quantified using cell-based segmentation, which provides a context for repair measurements and colocalization analysis. For enhanced robustness, cell-based segmentation and protein localization leverage geometric methods. Subsequently, cellular profiles are stored in a database, where colocalization analysis takes place through specially design database queries.