Polypeptide synthesis in enucleated mouse fibroblasts

The polypeptides synthesized in cytoplasts prepared from mouse L929 cells by cytochalasin-induced enucleation were analyzed by two-dimensional gel electrophoresis. Nearly all detectable polypeptides made in parental whole cells were likewise made in cytoplasts, though in decreasing amounts, for up to at least 12 hours after enucleation. A similar analysis of cells treated with actinomycin D, an inhibitor of transcription, showed that such cells initially synthesized all of the polypeptides made by untreated cells. However, by 12 hours after treatment, the electrophoretic patterns produced by preparations of radiolabeled cells were highly aberrant, with some polypeptides apparently greatly overproduced relative to others. The results are consistent with the notion that physical removal of the nucleus disrupts the mechanisms regulating mRNA degradation in eukaryotic cells.