pp135 was constitutively tyrosine-phosphorylated and associated with Shc and Bcr-Abl in CML cell lines. The lysates from three human CML (K562, Kcl22, and SKH1) and human AML (HL-60) cell lines were mixed with anti-Shc (A) or anti-P6 antibody (B). The resulting precipitates were subjected to SDS-PAGE and immunoblotted with anti-Py (top panels) and reprobed with anti-P6 (bottom panel of A). The lysates from these CML cell lines were also mixed with anti-Abl antibody (C). The precipitates were subjected to SDS-PAGE and immunoblotted with anti-Py (top panel) and reprobed with anti-P6 (bottom panel). The arrow indicates the position of pp135 and pp145. Molecular weight markers, indicated at the left, are given in kilodaltons.