Calculating the Degradation Rate of Individual Proteins Using Xenopus Extract Systems

The Use of Cell-Free Xenopus Extracts to Investigate Cytoplasmic Events

Experiments using cytoplasmic extracts prepared from Xenopus eggs have made important contributions to our understanding of the cell cycle, the cytoskeleton, and cytoplasmic membrane systems. Here we introduce the extract system and describe methods for visualizing and manipulating diverse cytoplasmic processes, and for assaying the functions, dynamics, and stability of individual factors. These in vitro approaches uniquely enable investigation of events at specific cell cycle states, including the assembly of actin- and microtubule-based structures, and the formation of the endoplasmic reticulum. Maternal stockpiles in extracts recapitulate diverse processes in the near absence of gene expression, and this biochemical system combined with microscopy empowers a wide range of mechanistic investigations.

Assessing Ubiquitylation of Individual Proteins Using Xenopus Extract Systems

Xenopus extract systems have been used to study ubiquitylation of proteins, and to uncover some of the fundamental processes of the ubiquitylation pathway itself. They provide a simple, quick, and robust method for studying ubiquitylation. In this protocol, methods are provided for studying protein ubiquitylation using Xenopus egg or embryo extracts and in vitro radiolabeled proteins. These methods also enable examination of whether proteins undergo noncanonical ubiquitylation, through modification of the protein by covalent linkage to ubiquitin through residues other than lysine, such as cysteine, serine, and threonine.