Controlling the stability of cellular proteins is a fundamental way by which cells regulate growth, differentiation, survival, and development. Measuring the turnover rate of a protein is often the first step in assessing whether or not the function of a protein is regulated by proteolysis under specific physiological conditions. Over the years, procedures to determine the half-life of proteins in cultured eukaryotic cells have been well-established. This chapter describes in detail the two most frequently used methods, pulse-chase analysis and cycloheximide blocking, to determine a protein's half-life in yeast and cultured mammalian cells.
