TEL-JAK2 fusion proteins are constitutively tyrosine phosphorylated in Ba/F3 cells.

(A) The characterized TEL-JAK2 fusions and the wild-type forms of TEL and JAK2. The breakpoints involved in the TEL-JAK2 chromosomal translocations are indicated by arrows. The TEL-JAK2(4-17) translocation fused nucleotide (nt) 463 of TEL to nt 2126 of JAK2, whereas TEL-JAK2(5-19) and TEL-JAK2(5-12) resulted in the fusion of TEL nt 1009 to JAK2 nt 2426 and JAK2 nt 1506, respectively. The 3 fusion proteins also contain a Myc-tag at the carboxy (C-) terminus. (B) Ba/F3 cells expressing the indicated TEL-JAK2 constructs were depleted of cytokine and then stimulated in the presence (+) or absence (−) of 10 ng/mL IL-3. IPs were performed with a pan-JAK antibody, and tyrosine-phosphorylated proteins were detected by IB with pTyr antibody.