Figure 4.

Tools that can be used to study Htt ubiquitination and degradation. (A) BioID and (B) APEX can be used to identify ubiquitin ligases and DUBs that putatively interact with Htt, as both techniques identify transient interacting proteins via promiscuous biotinylation of proteins in close proximity of the BirA* or APEX fusion protein. Biotinylated proteins can be purified using avidin/streptavidin beads and are subsequently identified by mass spectrometry. Figures adapted from Ueda et al. (2015) and Chu et al. (2017). (C) PROTACs can be used to induce ubiquitination of a protein of interest followed by proteasome-dependent degradation. PROTACs bring together the protein of interest (Htt in this case) and a ubiquitin ligase, leading to ubiquitination of the protein of interest and subsequent proteasome-dependent degradation.