Regulation of the c-jun Gene in p210 BCR-ABL Transformed Cells Corresponds With Activity of JNK, the c-jun N-Terminal Kinase

Abstract

Activity of the c-jun N-terminal kinase (JNK) has been shown in hematopoietic cells transformed by p210 BCR-ABL. However, analysis has not been reported for hematopoietic cells on the consequences of this activity for c-jun promoter regulation within its distinctive proximal 8-base consensus CRE-like element, an element linked to JNK-mediated increase in c-jun transcription. In the present study, regulation of the proximal c-jun promoter was studied in murine myeloid cells transformed by p210 BCR-ABL. Promoter regulation in p210 BCR-ABL transformed cells was compared with regulation of the promoter in nontransformed interleukin-3 (IL-3)–dependent parental cells. The composition of nuclear AP-1 proteins contained within cells with p210 BCR-ABL, and their binding to the c-jun promoter proximal CRE-like element, was compared with the composition and binding of AP-1 proteins in IL-3–treated parental cells without p210 BCR-ABL. The present analysis found fivefold increased c-jun transcription occurring in p210 BCR-ABL transformed murine myeloid cells possessing a corresponding magnitude of increased kinase activity of JNK, compared with IL-3–stimulated parental cells. Augmented JNK activity was accompanied by increased nuclear abundance of c-jun and c-fos proteins that bound specifically to the proximal c-jun promoter CRE element. Also, representative human leukemic cell lines expressing p210 BCR-ABL and possessing abundant kinase activity of JNK, when compared with parental cells that were deficient in JNK activity, had increased c-jun and c-fosproteins. Finally, to show the relevance of these observations in model systems, we studied blast cells from patients with Philadelphia chromosome–positive acute leukemic transformation, and observed comparable activities of JNK catalysis and c-jun/AP-1 protein relative to the cell lines that possessed p210 BCR-ABL and JNK activity. These studies provide a basis for investigating the set of downstream genes which augmented c-jun/AP-1 activity enlists in the process of transformation by p210 BCR-ABL.