UC Irvine

HeLa cells were found to enter and complete mitosis in the presence of puromycin or actinomycin D. Daughter cells formed in the presence of puromycin contained completed nuclear membranes. Daughter cells resumed protein synthesis shortly after completing mitosis however, this resumption of protein synthesis could be prevented by actinomycin D. Data presented here indicate that all cellular constituents necessary for successful initiation and completion of mitosis are produced prior to the onset of mitosis. They also indicate that new messenger RNA synthesis is required for resumption of protein synthesis after mitosis, and that the inhibition of protein synthesis observed in mitotic mammalian cells 18 a result of messer ger RNA depletion. © 1967.