FIG. 5.

SOCS-1 coexpression enhances proteasomal degradation of Jak2WT but not Jak2YF. Cos-7 cells were transiently transfected with plasmids encoding Jak2WT-HA (A and B) or Jak2YF-HA (C) either alone or together with plasmids encoding SOCS-1. After 48 h the cells were starved overnight and pretreated with proteasome inhibitor MG132 (20 μM) for 1 h before pervanadate treatment (25 μM). Jak2 was analyzed by immunoprecipitation (IP) with an anti-HA antibody followed by immunoblotting with the indicated antibodies. (A, a and b) Different exposures of the same blot. SOCS-1 protein levels were determined by Western blotting 20 μg of total-cell lysates using an anti-SOCS-1 antibody.