Fig. 2.

Diagrammatic representation of the ubiquitin pathway and the components, where SMN interacts. SMN is both ubiquitinated via the UPS pathway and an interacting protein influencing several steps of the process. SMN directly interacts with the UBA1 enzyme, which transfers ubiquitin to the E2 ligases. Ubiquitinated E2 ligases then form a complex with E3 ligases bound to protein substrates. SMN has been shown to interact with several E3 ligases, including Mindbomb 1, Itch and TRAF6. Ubiquitin is then transferred to the protein substrate and the complex dissociates. Monoubiquitinated substrates continue on to other intracellular processes, whereas polyubiquitinated substrates are targeted for proteasome degradation. SMN has also been shown to interact with deubiquitinating enzymes, which remove ubiquitin from protein substrates