Ubiquitylation affects proteins in many ways, such as activation or inactivation, and signaling for their degradation. It is not fully understood how ubiquitin effects all proteins or how researchers may use it to control cellular processes. This invention describes novel fusion proteins that protect ubiquitylated forms of the target proteins from degradation.
Ubiquitylation of proteins can be a signal for a variety of cellular processes beyond the classical role in protein degradation, known as proteolysis. The different signaling functions of ubiquitylation are thought to rely on ubiquitin-binding domains (UBDs). However, little is known regarding the mechanism by which UBDs are able to protect ubiquitylated proteins from degradation.
Through studying the yeast protein Met4, researchers at UCI have uncovered a unique UBD that can be utilized to probe the ubiquitinylation and degradation processes. The sequence found in Met4 is a region of tandem UBDs, containing previously discovered motifs and a novel binding region. This invention describes an unprecedented method for protecting ubiquitylated proteins from degradation by fusion to this unique UBD. This approach enables the enrichment of target proteins, the study of the structure-function relationships of ubiquitin-modified proteins, and ultimately the understanding and control of the ubiquitin-protease pathway.
§ Identifies a unique mechanism of protecting ubiquitin-modified fusion proteins
§ Stabilizes the binding partner of the fusion protein and also protects it from degradation
§ Enables determination of ubiquitylated proteins
§ Allows for characterization of protein function after ubiquitylation
§ Could be developed as a technology to control or induce degradation of a protein at will
A fusion of Met4 tandem UBDs to the classic proteasome substrate Sic1 was generated. The UBD fusion was shown to prevent it further elongation of ubiquitin chains in vitro and to stabilize polyubiquitylated Sic1 in vivo.