Researchers crack the code of protein degradation

Using UbiREAD (Ubiquitinated Reporter Evaluation After intracellular Delivery), research groups led by Brenda Schulman (MPIB) and Leo Kiss (MRC) labeled fluorescent proteins with specific ubiquitin codes and tracked their degradation in cells, revealing how tags mark specific proteins for intracellular degradation. By measuring fluorescence intensity, which correlates with the protein quantity, they tracked the degradation dynamics.

Key discoveries included the finding that intracellular degradation is faster than assessed with in vitro degradation assays. It took only a minute to degrade half of the tagged protein in cellular environment. In addition, the researchers demonstrated that proteins tagged with the ubiquitin chain K48 are rapidly degraded, while proteins tagged with K63 quickly lose their tag and avoid proteolysis.

Brenda Schulman, Director at the MPIB, stated: “Our findings highlight the importance of investigating ubiquitin chains and their functions in their native cellular environment. We have shown that UbiREAD is a versatile tool to analyse intracellular degradation of proteins conjugated to various types of ubiquitin or ubiquitin-like protein chains in different cellular contexts. In the near future, we will continue to use the method to gain many more insights into the complex ubiquitin system.”