Stat signaling specificity of chimeric EpoR. 32D cells expressing R129C, R129C/343-S3, R129C/401-S3, or R129C/343/401-S3 were cultured in RPMI for 4 h, then stimulated with 20 U/ml Epo for 8 min at 37°C. Stat3 (lanes 1, 3, 5, 7) and Stat5 (lanes 2, 4, 6, 8) were immunoprecipitated from detergent cell extracts, and proteins were analyzed by antiphosphotyrosine immunoblots. A digital image of the autora-diogram is shown.