Stony Brook University, State University of New York 1 article published in JoVE Biology Assaying Proteasomal Degradation in a Cell-free System in Plants Elena García-Cano1, Adi Zaltsman1, Vitaly Citovsky1 1Department of Biochemistry and Cell Biology, Stony Brook University, State University of New York Targeted protein degradation represents a major regulatory mechanism for cell function. It occurs via a conserved ubiquitin-proteasome pathway, which attaches polyubiquitin chains to the target protein that then serve as molecular “tags” for the 26S proteasome. Here, we describe a simple and reliable cell-free assay for proteasomal degradation of proteins.