Induction and/or selective retention of proteins in mammalian cells exposed to cycloheximide

Abstract

Exposure of a number of murine and human cell lines to low graded doses of cycloheximide (CXM) results in a pattern of protein synthesis consisting of enhanced and induced species. These can be divided into two main classes according to molecular weight (20-40 and 70-120 Kd), similar to what has been described for other agents that modify the physiological conditions of growth. In addition, the pronounced synthesis of a hitherto unreported 50-Kd protein species has been consistently observed in all lines tested. Simultaneous exposure of cells to CXM and actinomycin D results in suppressing synthesis of some but not all protein species observed, indicating that control mechanisms at both transcriptional and posttranscriptional levels may be operative in this system.

Induction of the five urea-cycle enzymes by glucagon in cultured foetal rat hepatocytes

“…In fact, contrary to what had been expected, it reinforced the action of glucagon. This effect was obtained at all of the tested concentrations (0.5-30 pg/ml; data not shown), such findings have already, been reported for phosphoenolpyruvate carboxykinase [2] and several other proteins [33]. This result might be explained by the compound acting against the degradation of proteins 191 or against mRNA degradation PI.…”

Cycloheximide protection against actinomycin D cytotoxicity

“…CHM also stabilizes short-lived mRNA against degradation (Sorrentino et al, 1985;Denhardt, 1986). Thus the increase in cytoplasmic c-myc mRNA may have been the result of both continued transcription and greater stability against degradation.…”

“…It has been postulated that CHM increases cytoplasmic levels of some RNA species by inhibiting translation of the corresponding protein, which in turn functions as a feedback regulator of transcription (Sorrentino et al, 1985;Denhardt, 1986). CHM also stabilizes short-lived mRNA against degradation (Sorrentino et al, 1985;Denhardt, 1986). Thus the increase in cytoplasmic c-myc mRNA may have been the result of both continued transcription and greater stability against degradation.…”

“…The amounts of intracellular free drug and drug bound to the acid precipitable cell fraction were determined. CHM elevates and/or stabilizes cytoplasmic levels of certain mRNA species (Sorrentino et al, 1985;Denhardt et al, 1986), which may include essential mRNA whose cytoplasmic levels are depleted by AD. The reduction of such mRNA may represent a lethal lesion, whereas stabilizat.ion and/or elevation of their cytoplasmic levels may be one means by which CHM counter-acts a lethal effect of AD.…”

Posttranscriptional control of human gamma interferon gene expression in transfected mouse fibroblasts.

“…Similar results have been obtained when a human immunoglobulin heavy-chain genomic DNA clone was transfected into mouse L cells (11), indicating that treatment of mouse fibroblasts with protein synthesis inhibitors can overcome tissue-specific restriction of gene expression. In addition, cycloheximide has been shown to stimulate early adenovirus transcription (3), c-myc transcription (13), histone mRNA synthesis (21), and the synthesis of new proteins in mouse fibroblasts (10,19). We have now observed that the restriction of the protein expression of the human IFN--y gene observed after introduction of this T-cell-and large-granularlymphocyte-specific gene into mouse fibroblasts can be overcome with protein synthesis inhibitors.…”