TSG101 and prion disease: MGRN1 is known to multi-monoubiquitinate TSG101, affect its solubility and hypothesized to have a key role in the pathogenesis of spongiform encephalopathy in Mgrn1 null mice.22, 41 Induction of autophagic flux was used as a read-out to test the significance of MGRN1-mediated monoubiquitination of TSG101 in regulating vesicular fusion with lysosomes (Figure 7a(i)).