Constitutive expression of TEL/PDGFβR in BaF/3 cells. BaF/3 tTA cells were transfected with pcDNA3.1 encoding TEL/PDGFβR. (A) Immunoblot showing an example of expression of TEL/PDGFβR in antibiotic-resistant clones selected. (B) The same blot as in panel A was stripped and reprobed to detect tyrosine phosphorylated proteins. (C) The same blot as in panels A and B was stripped and reprobed with anti–SHP-2 antibodies to assess equality of loading. (D) Constitutively expressing clones cTP11, cTP14, and cTP15 or parental BaF/3 tTA were washed and incubated for 8 days in media lacking IL-3. The percentage of viable cells was determined at the times indicated using trypan blue exclusion. (E) BaF/3 tTA (BaF/3) or constitutively expressing factor-independent clone cTP14FI was incubated for 1 hour in the presence or absence of serum prior to preparation of cell lysates. Immunoblotting was performed with 4G10 to detect tyrosine phosphorylated proteins (pTyr) and the blot was stripped and reprobed to with anti-PDGFβR antibodies to detect TEL/PDGFβR.