benzyloxycarbonylleucyl-leucyl-leucine-aldehyde and Leukemia--Erythroblastic--Acute

Growth-inhibitory effects on DS19 mouse erythroleukemia cells were seen in the micromolar concentration range with allicin and S-allylmercaptocysteine and in the millimolar range with allyl butyrate, allyl phenyl sulfone, and S-allyl cysteine. Increased acetylation of histones was induced by incubation of cells with the allyl compounds at concentrations similar to those that resulted in the inhibition of cell proliferation. The induction of histone acetylation by S-allylmercaptocysteine was also observed in Caco-2 human colon cancer cells and T47D human breast cancer cells. In contrast to the effect on histone acetylation, there was a decrease in the incorporation of phosphate into histones when DS19 cells were incubated with 25 microM S-allylmercaptocysteine. Histone deacetylase activity was inhibited by allyl butyrate, but there was little or no effect with the allyl sulfur compounds examined in this study. A similar degree of downregulation of histone deacetylase and histone acetyltransferase was observed when DS19 cells were incubated with S-allylmercaptocysteine or allyl isothiocyanate. The induction of histone acetylation by S-allylmercaptocysteine was not blocked by a proteasome inhibitor. The mechanism by which S-allylmercaptocysteine induces histone acetylation remains to be characterized. It may be related in part to metabolism to allyl mercaptan, which is a more effective inhibitor of histone deacetylase.

Topics: Acetylation; Acetyltransferases; Allyl Compounds; Animals; Antineoplastic Agents; Breast Neoplasms; Colonic Neoplasms; Cysteine; Disulfides; Electrophoresis, Polyacrylamide Gel; Female; Histone Acetyltransferases; Histone Deacetylases; Histones; Humans; Leukemia, Erythroblastic, Acute; Leupeptins; Mice; Saccharomyces cerevisiae Proteins; Sulfinic Acids; Tumor Cells, Cultured

Mammalian cells coexpress a family of heat shock factors (HSFs) whose activities are regulated by diverse stress conditions to coordinate the inducible expression of heat shock genes. Distinct from HSF1, which is expressed ubiquitously and activated by heat shock and other stresses that result in the appearance of nonnative proteins, the stress signal for HSF2 has not been identified. HSF2 activity has been associated with development and differentiation, and the activation properties of HSF2 have been characterized in hemin-treated human K562 erythroleukemia cells. Here, we demonstrate that a stress signal for HSF2 activation occurs when the ubiquitin-proteasome pathway is inhibited. HSF2 DNA-binding activity is induced upon exposure of mammalian cells to the proteasome inhibitors hemin, MG132, and lactacystin, and in the mouse ts85 cell line, which carries a temperature sensitivity mutation in the ubiquitin-activating enzyme (E1) upon shift to the nonpermissive temperature. HSF2 is labile, and its activation requires both continued protein synthesis and reduced degradation. The downstream effect of HSF2 activation by proteasome inhibitors is the induction of the same set of heat shock genes that are induced during heat shock by HSF1, thus revealing that HSF2 affords the cell with a novel heat shock gene-regulatory mechanism to respond to changes in the protein-degradative machinery.

Topics: Animals; Cell Line; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors; Fibroblasts; Gene Expression Regulation; Heat-Shock Proteins; HeLa Cells; Hemin; Humans; Kinetics; Leukemia, Erythroblastic, Acute; Leupeptins; Mammals; Mice; Multienzyme Complexes; Proteasome Endopeptidase Complex; Transcription Factors; Tumor Cells, Cultured; Ubiquitins