CISPLATIN INHIBITS PROTEIN-SYNTHESIS IN RABBIT RETICULOCYTE LYSATE BYCAUSING AN ARREST IN ELONGATION

The mechanism through which cisplatin (cis-diamminedichloroplatinum) i nhibits protein synthesis in rabbit reticulocyte. lysate was character ized, Cisplatin and transplatin caused a progressive slowing in the ra te of protein synthesis culminating in the complete arrest of translat ion, Inhibition was dependent upon the aquation of the compounds. Addi tion of eukaryotic initiation factor eIF-2, eIF-2B, cAMP, MgGTP, or di thiothreitol neither prevented nor reversed the inhibition induced by cisplatin, indicating that the mechanism of cisplatin-induced translat ional inhibition is distinct from the inhibition induced by other toxi c heavy metal ions (Hurst, R., Schatz, J. R., and Matts, R. L. (1987) J. Biol. Chem, 262, 15939-15945; Matts, R. L., Schatz, J. R., Hurst, R ., and Kagen, R. (1991) J. Biol. Chem. 266, 12695-12702). Analysis of the polyribosome profile of cisplatin-inhibited reticulocyte lysate in dicated that cisplatin arrests the elongation stage of protein synthes is, Agarose gel electrophoresis and Northern blot analysis indicated t hat mRNA and rRNA become crosslinked to form very high-molecular-weigh t adducts upon extraction of the RNA from polyribosomes of cisplatin-t reated lysates, Diethyldithiocarbamate, which reduces the cytotoxicity of cisplatin in vivo, protects protein synthesis in reticulocyte lysa te from inhibition by cisplatin. The data suggest that extensive deriv atization of reticulocyte lysate RNA by cis- and transplatin results i ll the arrest of translating ribosomes. Since arrest of translational elongation is a well-defined mechanism of action of several families o f toxins, we suggest that it may contribute to the cytotoxic action of cisplatin observed in certain populations of cells. (C) 1997 Academic Press.