FIG. 3.

Tyrosine phosphorylation of Jak2 correlates with its ubiquitination and degradation. Jak2WT-HA (left) and Jak2KN-HA (right) were transiently expressed in Cos-7 cells. After 48 h the cells were starved overnight and pretreated with proteasome inhibitor β-lactacystin (20 μM) or vehicle for 1 h before treatment with different concentrations of pervanadate for 1 h. Total-cell lysates were immunoprecipitated (IP) with an anti-HA antibody and analyzed by immunoblotting using antiubiquitin or antiphosphotyrosine (anti-PTyr) antibodies. The antiubiquitin and antiphosphotyrosine blots from Jak2WT-HA and Jak2KN-HA panels were exposed for the same time. The filters were then stripped and blotted with an anti-HA antibody (bottom).