Role of MAPK in the regulation of HNRPK expression in BCR/ABL⁺ cells. (A) Effect of different chemical inhibitors of known BCR/ABL-activated pathways on HNRPK protein levels in 32D-BCR/ABL and K562 cells. (B) Effect of the MEK1/MAPK inhibitor PD098059 (lane 2) on Hnrpk mRNA (first row) and protein (third row) expression. Hnrpk mRNA (first row) and protein (third row) levels in parental 32Dcl3 cells (lane 3), vector-transduced 32D-BCR/ABL (lane 4), and 32D-BCR/ABL cells ectopically expressing wild-type MAPK ERK1 (lane 5), the K71R dominant-negative MAPK ERK1 mutant (lane 6), wild-type ERK2 (lane 7), and dominant-negative K52R ERK2 mutant (lane 8). rRNA and GRB2 are shown as controls for equal loading. (C) Effect of BCR/ABL tyrosine kinase on MAPK/ERK activity. pERK1/2 indicates phosphorylated (active) ERK1 and ERK2 mitogen-activated protein kinases. Western blots show levels of HNRPK, phospho-ERK1/2, total ERK1/2, BCR/ABL, and GRB2 in 32Dcl3 myeloid precursors transduced with a GFP/BCR/ABL bicistronic retrovirus and sorted for low, medium, and high GFP levels. (D) Levels of HNRPK, phospho-ERK1/2, BCR/ABL, and GRB2 in mononuclear marrow cells from paired chronic phase (CP) and blast crisis (BC) CML patient samples. (E) Levels of pERK1/2, ERK1/2, and GRB2 in NBM^CD34+, CML-CP^CD34+, CML-AP^CD34+, and CML-BC^CD34+samples.