Bcl-2- and CrmA-inhibitable dephosphorylation and cleavage of retinoblastoma protein during etoposide-induced apoptosis.
Cell numbers are regulated by a balance between proliferation and apoptosis (programmed cell death). Recent evidence suggests that proteins regulating cell proliferation also mediate apoptosis. Therefore, cellular fate might be determined by cross talk between regulators of cell cycle progression and apoptosis. Previously, we had found that during DNA damage-induced apoptosis, retinoblastoma protein (RB), an important G1/S regulator and tumor suppressor, became dephosphorylated and then immediately cleaved into p48 and p68 fragments. Here, we report that expression of the Bcl-2 oncoprotein, an inhibitor of caspases (interleukin 1 -converting enzyme-like proteases), blocked RB dephosphorylation, RB cleavage and apoptosis in etoposide-treated human Jurkat T cells. In addition, expression of the cowpox virus CrmA protein, a direct inhibitor of caspases, also inhibited both RB changes and apoptosis. Taken together, our findings demonstrate important roles for caspases in the processes of etoposide-induced RB dephosphorylation, RB proteolysis and apoptosis.
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Document Type: Research Article
Affiliations: Department of Pharmacology, University of Pittsburgh School of Medicine and University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213-2582, USA.
Publication date: January 1, 1998
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- The International Journal of Molecular Medicine is a monthly, peer-reviewed journal devoted to the publication of high quality studies related to the molecular mechanisms of human disease. The journal welcomes research on all aspects of molecular and clinical research, ranging from biochemistry to immunology, pathology, genetics, human genomics, microbiology, molecular pathogenesis, molecular cardiology, molecular surgery and molecular psychology.
The International Journal of Molecular Medicine aims to provide an insight for researchers within the community in regard to developing molecular tools and identifying molecular targets for the diagnosis and treatment of a diverse number of human diseases.
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