Hpo stabilises Sav by inhibiting Sav ubiquitylation.

(A) Sav is stabilised when co-expressed with Hpo. Baseline Sav expression is increased upon proteasome inhibitor treatment (M/L). (B) hpo depletion by RNAi destabilises Sav protein levels. Top panel: endogenous Sav levels (arrow) in non-transfected S2 cells. Asterisk indicates a non-specific band detected by the anti-Sav antibody. Bottom panel: levels of transfected Myc-tagged Sav. Sav depletion by RNAi is used as a control. (C) Hpo inhibits ubiquitylation of Sav. Sav, Sav∆N, and Sav∆C were analysed for ubiquitylation in the presence or absence of co-expressed Hpo. Hpo prevents ubiquitylation of full-length Sav and Sav∆N, while Sav∆C is not ubiquitylated. (A-C) S2 cells were transfected with the indicated plasmids or treated with the indicated dsRNAs prior to lysis. Lysates were processed for western blot analysis or used in co-IP.