IndraLab

"USP13 and gp78 control ubiquitination of Ubl4A.These data suggest that USP13 and gp78 play antagonizing roles in regulation of Ubl4A ubiquitination: While gp78 assembles ubiquitin chains on Ubl4A, USP13 antagonizes this activity to limit Ubl4A ubiquitination.Ubiquitination of Ubl4A preferentially occurs on Lys48. We identify the Bag6 cofactor Ubl4A as a shared substrate of gp78 and USP13. USP13 depletion is associated with hyper-ubiquitination of Ubl4A and altered interaction between the Bag6 complex and its co-chaperone SGTA. Because the interaction of Ubl4A with SGTA is mediated by positively-charged residues in Ubl4A including Lys48 (Chartron et al., 2012; Xu et al., 2012), which happens to be the major ubiquitination site, the simplest model to explain reduced Bag6-SGTA interaction in USP13 knockdown cells is that ubiquitin conjugates on Ubl4A sterically hinder SGTA binding."