Using an ImageJ-based script to detect replication stress and associated cell cycle exit from G2 phase by fluorescence microscopy

Replication stress risks genomic integrity. Depending on the level, replication stress can lead to slower progression through S phase and entry into G2 phase with DNA damage. In G2 phase, cells either recover and eventually enter mitosis or permanently withdraw from the cell cycle. Here we describe a method to detect cell cycle distribution, replication stress and cell cycle exit from G2 phase using fluorescence microscopy. We provide a script to automate the analysis using ImageJ. The focus has been to make a script and setup that is accessible to people without extensive computer knowledge.