Tyrosine phosphorylation and kinase activity of Jak2 are inhibited by PKC-δ.

(A) COS7 cells were transfected with HA-tagged Jak2 and PKC-δ expression plasmids, as indicated. Jak2 was immunoprecipitated with anti-HA antibody and subjected to anti-phosphotyrosine and subsequently anti-HA immunoblotting. (B) COS7 cells were transfected with Jak2, PKC-δ, and PKC-ζ expression plasmids, as indicated. Jak2 was immunoprecipitated and subjected to in vitro kinase assay using Stat1 tyrosine phosphorylation-site peptide as substrate. The reactions were separated on 20% SDS-PAGE, followed by autoradiography.