TEL-Jak2 JH1 and TEL-Jak2 JH2+JH1 are constitutively tyrosine-phosphorylated in COS cells. COS cells were transfected with the constructs as indicated. Fifty micrograms of lysate was resolved via SDS-PAGE and transferred to nitrocellulose. The membrane was incubated with a monoclonal antiphosphotyrosine antibody followed by HRP-sheep antimouse IgG. The position of each tyrosine-phosphorylated protein and molecular weight standards are indicated.