Reagents
The polyclonal STAT5a-specific and STAT5b-specific antibodies were developed in our laboratory, as previously described [23]. Polyclonal anti-STAT3 antibodies, polyclonal anti-Brk antibodies, and monoclonal antiphosphotyrosine antibodies (PY-99) were obtained from Santa Cruz Biotechnology (Santa Cruz, CA, USA). The monoclonal anti-β-actin antibody was from Sigma (St Louis, MO, USA). The antiphospho-STAT5a/b (Y694/Y699) antibody was developed in conjunction with Aves Labs (Tigand, OR, USA) as described elsewhere (EM Fox, T Bernaciak, J Wen, A Weaver, M Shupnik, CM Silva - unpublished data). The protease inhibitor cocktail was from Calbiochem (San Diego, CA, USA). The acrylamide was obtained from Bio-Rad (Hercules, CA, USA), and the prestained molecular weight marker was from Invitrogen. Except as noted, other reagents were of either reagent grade or molecular biological grade from Sigma.