The actinomycin D-induced apoptosis in BCR-ABL-positive K562 cells is associated with cytoplasmic translocation and cleavage of RNA helicase A.

K562 cells express the fusion protein BCR-ABL and have been shown to be relatively more resistant to apoptosis induction by chemotherapeutic agents. We show that Actinomycin D (Act D) induces time- and dose-dependent apoptosis in K562 cells. Act D causes early activation of caspase-3 followed by inhibition of the expression of the anti-apoptotic proteins BCR-ABL and Bcl-xl. Act D-induced apoptosis is associated with cytoplasmic translocation and cleavage of the multifunctional nuclear protein RNA helicase A (RHA). RHA has roles in transcription and RNA metabolism and has been shown to be cleaved during Fas mediated apoptosis. These results suggest that Act D causes caspase-3 activation and apoptosis in BCR-ABL positive K562 cells and that RHA cytoplasmic translocation and cleavage occur in chemotherapy-induced apoptosis.