Ribonucleic acid metabolism in lymphocytes stimulated by phytohemagglutinin. II. Rapidly synthesized ribonucleic acid and te production of ribosomal ribonucleic acid.
نویسنده
چکیده
Human peripheral lymphocytes are stimulated to change, in vitro, from a resting state to one of progressive enlargement, culminating in mitosis, by treatment with Phaseolus vulgaris phytohemagglutinin. The sedimentation characteristics and fate of rapidly synthesized RNA have been studied in this system after 20 hours of stimulation with phytohemagglutinin, a time when RNA synthesis has been accelerated but DNA synthesis has not begun. The following findings are reported. 1. RNA synthesized during any short interval was found to be largely polydisperse in sedimentation behavior, with s values predominantly greater than 28 S. This material did not serve as a macromolecular precursor to ribosomal RNA or to other discretely sedimenting RNA species. Base composition determinations, by z2P incorporation, indicated that this material was neither ribosome-like nor DNA-like, since it had a high uridylate and low adenylate content. Estimates of the half-life of the polydisperse RNA gave a range of + to 2 hours. 2. The sequence of events in the production of ribosomal RNA was examined in detail in the lymphocyte system and was found to be essentially similar to that reported for HeLa cells: a 45 S precursor is converted, during a period of 15 min, to 32 S and 18 S molecules. The 32 S molecule is then converted, during the next 1 to 2 hours, to the 28 S ribosomal RNA. 3. Lymphocytes were found to be relatively resistant to the effects of actinomycin D, requiring longer times of exposure, and larger doses, to produce the inhibitory effects on RNA synthesis which have been reported with other cell systems.
منابع مشابه
Characteristics of the RNA Synthesized in Vitro by the Normal Human Small Lymphocyte and the Changes Induced by Phytohemagglutinin Stimulation UMBERTO
A B S T R A C T These studies demonstrate that the circulating human small lymphocyte synthesizes ribonucleic acid (RNA) of high molecular weight which is not primarily a ribosomal precursor and which is, in part, complementary to human deoxyribonucleic acid (DNA). The stimulation of these lymphocytes by PHA brings a cell population in which few ribosomes are synthesized to a functional conditi...
متن کاملCharacteristics of the RNA synthesized in vitro by the normal human small lymphocyte and the changes induced by phytohemagglutinin stimulation.
These studies demonstrate that the circulating human small lymphocyte synthesizes ribonucleic acid (RNA) of high molecular weight which is not primarily a ribosomal precursor and which is, in part, complementary to human deoxyribonucleic acid (DNA). The stimulation of these lymphocytes by PHA brings a cell population in which few ribosomes are synthesized to a functional condition in which a la...
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ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 243 1 شماره
صفحات -
تاریخ انتشار 1968