Multiple approaches to study S. cerevisiae Rad9, a prototypical checkpoint protein.

The Saccharomyces cerevisiae RAD9 checkpoint gene is the prototypical checkpoint gene and is required for efficient checkpoint regulation in late G1, S, and at the G2/M cell cycle transition following DNA damage. Rad9 is required for the activation of Rad53 after damage and has been proposed to have roles in lesion recognition as well as DNA repair and the maintenance of genome stability. Here we describe methodology suitable for the study of G1, intra-S, and G2/M checkpoints in budding yeast, the analysis of Rad9/Rad53 phospho-forms, the biochemical analysis of Rad9 and Rad53, the fractionation of soluble and chromatin associated proteins, including Rad9, and the live cell imaging of GFP tagged Rad9.