Etoposide is an extensively prescribed anticancer drug that, unfortunately, causes therapy-related leukemia. The mechanisms by which etoposide induces secondary hematopoietic malignancies are poorly documented. However, etoposide-related leukemogenesis is known to depend on oxidative metabolites of etoposide, notably etoposide quinone, that can react with protein cysteine residues such as in topoisomerases II. CREBBP is a major histone acetyltransferase that functions mainly as a transcriptional co-activator. This epigenetic enzyme is considered as a tumor suppressor that plays a major role in hematopoiesis. Genetic alterations affecting CREBBP activity are highly common in hematopoietic malignancies. We report here that CREBBP is impaired by etoposide quinone. Molecular and kinetic analyses show that this inhibition occurs through the rapid and covalent (k=16.10 M. s) adduction of etoposide quinone with redox sensitive cysteine residues within the RING and PHD Zn-fingers of CREBBP catalytic core leading to subsequent release of Zn. In agreement with these findings, experiments conducted in cells and in mice treated with etoposide showed irreversible inhibition of endogenous CREBBP activity and decreased H3K18 and H3K27 acetylation. As shown for topoisomerases II, our work thus suggests that the leukemogenic metabolite etoposide quinone can impair the epigenetic CREBBP acetyltransferase through reaction with redox sensitive cysteine residues.
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