ERK-dependent phosphorylation controls hnRNP-E2 protein stability. (A) hnRNP-E2 expression in parental and BCR/ABL-transduced 32Dcl3 cells expressing an empty vector, HA-hnRNP-E2, HA-hnRNP-E2^{S173A,S189A,T213A,S272A} (Ser/Thr→Ala), and HA-hnRNP-E2^{S173D,S189D,T213E,S272D} (Ser/Thr→Asp/Glu). Cells were IL-3 deprived for 8 hours. (B) Stability of newly synthesized HA-tagged hnRNP-E2, hnRNP-E2^{S173A,S189A,T213A,S272A}, and hnRNP-E2^{S173D,S189D,T213E,S272D} in ³⁵S-labeled 32D-BCR/ABL cells. The half-life of hnRNP-E2 was assessed by pulse-chase assay and quantified by densitometry. Each point on the graph represents the relative normalized amounts of hnRNP-E2 during the chase period. (C) Stability of HA-tagged hnRNP-E2, hnRNP-E2^{S173A,S189A,T213A,S272A}, and hnRNP-E2^{S173D,S189D,T213E,S272D} in 32D-BCR/ABL cells treated with cycloheximide (CHX). HSP90 levels were used as control for equal loading.