Regulation of Protein Synthesis in Chick Oviduct

Norman K. Wessells: a life in science

"In its triple role as locomotory organelle, as a site of deposition of new surface material for the elongating axon, and a source of microspikes (sensory probes), the growth cone becomes the key to axon elongation" Yamada et al. (1971).

The use of a reversible transcription inhibitor, DRB, to investigate the involvement of specific proteins in the ocular circadian system of Aplysia

Previously, the effects of 2-h treatments with the reversible transcription inhibitor 5,6-dichloro-1-beta-D-ribobenzimidazole (DRB) on the phase of the circadian rhythm in the eye of Aplysia californica were studied. Here we report a study of the effects of DRB on protein synthesis and a more detailed investigation of the effects of DRB on the phase of the circadian rhythm. Treatments of DRB for 30 min reduced the rate of transcription to about 30% of control values, and this inhibition reversed completely within 2 h after the end of the treatment. A phase-response curve was obtained for 30-min treatments of DRB. Shorter (30 min) treatments with DRB produced phase shifts comparable to those produced by treatments with DRB for 2 h. The phase-response curve obtained using 30-min treatments of DRB was similar to one obtained using 2-h treatments with respect to the phase at which DRB exerts its maximum effect on the rhythm (around circadian time [CT] 6). However, some aspects of the two phase-response curves were different. The effect of DRB on the phase of the rhythm appeared rapidly after removal of DRB treatments given during CT 22-6, but the effects of DRB on the phase of the rhythm appeared more slowly (approximately 10 h) after the treatments given during CT 6-12. Because the effects of DRB on the phase of the overt rhythm appear to be rapid at a particular phase, it is very likely that DRB affects the phase of the rhythm by altering the synthesis of proteins during or shortly after the treatment. Thus we searched for proteins whose synthesis was altered by DRB. Incorporation of labeled amino acids into 2 proteins was found to be altered during the DRB treatment, whereas 15 proteins were affected after the DRB treatment. Among the proteins affected during or shortly after the DRB treatment were four previously identified proteins affected by other treatments that can shift the phase of the eye circadian rhythm. These four proteins are worthy of further study as possible candidates for components of the circadian oscillator.

Superinduction of ornithine decarboxylase (ODC) by actinomycin D is due to stimulation of ODC mRNA translation

Inhibition of transcription by treatment with actinomycin D caused superinduction of the ornithine decarboxylase (ODC) activity in Ehrlich ascites tumor cells. Experiments with cycloheximide ruled out the possibility that this superinduction was due to stabilization of ODC. Instead the ODC activity exhibited a more rapid turnover in the presence of actinomycin D (t1/2 = 56 min). The superinduction was found to coincide with an increased rate of ODC synthesis, as determined by measuring the incorporation of [35S )methionine into immunoreactive ODC protein. The steady-state level of ODC mRNA was unchanged, indicating an effect on the translational efficiency.

Cellular regulation of diphtheria toxin cell surface receptors

The cellular regulation of diphtheria toxin cell surface receptors was studied. Treatment of Vero cells with cycloheximide reduced their diphtheria toxin binding capacity, while cells treated with actinomycin D did not lose their ability to bind diphtheria toxin. A non-toxic analogue of diphtheria toxin, CRM 197, produced a dose-related depletion of cell surface diphtheria toxin binding capacity that was reversible upon washing the cells. Vero cells depleted of toxin receptors by CRM 197 did not restore their ability to bind diphtheria toxin in the presence of cycloheximide. Phospholipase C treatment of Vero cells reduced their diphtheria toxin binding capacity in a dose-dependent manner. The loss of diphtheria toxin binding capacity was recovered within 2 hr after removal of the enzyme. Protein synthesis inhibition blocked this recovery while actinomycin D partially inhibited it. Receptors prebound with toxin were resistant to phospholipase C treatment, suggesting that the action of the enzyme was directly on the receptor. Inhibition of glycosylation with tunicamycin did not prevent reappearance of toxin receptors after CRM 197 or phospholipase C treatment. These data establish the requirement of a continuous protein synthesis for the maintenance of diphtheria toxin cell surface receptors and also suggest that these receptors do not recycle after binding ligand. A hypothesis is put forward that the diphtheria toxin receptor might be a lipid-linked cell surface protein.

Treatment of Chinese hamster ovary cells with the transcriptional inhibitor actinomycin D inhibits binding of messenger RNA to ribosomes

Inhibitors of RNA synthesis such as actinomycin D, MPB, and cordycepin progressively inhibit the initiation of protein synthesis in intact, nucleated mammalian cells. This inhibition is not dependent on the levels of mRNA, ribosomes, or tRNA. Lysates prepared from CHO cells treated with actinomycin D do not incorporate labeled globin mRNA or ovalbumin mRNA into 80S initiation complexes at the rates of untreated control extract. The ability of the extracts to produce and accumulate 48S preinitiation complexes was assessed using the 60S subunit joining inhibitors edeine and 5'-guanylyl imidodiphosphate. Control extracts were able to accumulate both the 48S preinitiation complexes and the migration-related intermediates in the presence of both inhibitors. However, lysates derived from CHO cells treated with actinomycin D were unable to produce these complexes. This was also true at low temperature, a condition that does not inhibit mRNA binding but prevents migration of the 43S complex along the mRNA. Mixing experiments with extracts from untreated control or AMD-treated CHO cells provided no evidence for a translational inhibitor. Thus, our data are consistent with the hypothesis that treatment of whole cells with actinomycin D inhibits protein synthesis initiation at the level of mRNA binding and not at migration or 60S subunit joining.

Regulation of arachidonic acid metabolism in Madin-Darby canine kidney cells: stimulation of synthesis of the cyclooxygenase system by 12-O-tetradecanoyl-phorbol-13-acetate

Stimulation of Madin-Darby canine kidney cells by 12-O-tetradecanoyl-phorbol-13-acetate (TPA) results in an increase in prostaglandin synthesis. We have measured the specific activity of the cyclooxygenase system in a cell-free assay and demonstrate that a fourfold induction occurs by 6 h poststimulation. This induction could be prevented by continuous treatment with either cycloheximide or actinomycin D. When cycloheximide was added to cells 6 h post-TPA stimulation we found only a 50% reduction in prostaglandin synthesis over the ensuing 6 h in vitro; this decrease in activity was not observed when actinomycin was used. On the other hand, cells stimulated with TPA for 6 h and subsequently treated with cycloheximide or actinomycin D ceased prostaglandin synthesis completely within 1 h. These results suggest that TPA stimulation of prostaglandin synthesis requires both transcriptional and translational events but that a factor(s) in addition to or in place of the cyclooxygenase might be crucial.

Glucocorticoid-dependent uteroglobin synthesis and uteroglobulin mRNA levels in rabbit lung explants cultured in vitro

In rabbit lung explants cultured in vitro in a synthetic medium, the synthesis of the protein uteroglobin decayed progressively becoming virtually undetectable between 24-48 h of culture. Addition of glucocorticoids to the medium maintained the synthesis of uteroglobin. This glucocorticoid effect was dose-dependent with optima at about 0.1 microM and 1 microM for dexamethasone and cortisol respectively. Estradiol, progesterone, triiodothyronine, insulin or 10% calf serum added to the medium were ineffective in maintaining uteroglobin synthesis. Actinomycin D (10 micrograms/ml) added to the medium inhibited the effect of cortisol on uteroglobin synthesis. After 24 h of culture, both the relative levels of uteroglobin mRNA, measured by molecular hybridization, and uteroglobin synthesis were correlatively higher (up to 10-fold) in glucocorticoid-treated than in control explants.

RNA synthesis in activated macrophages I. Poly(I) X poly(C)-induced triggering of cytolytic activity is associated with decrease in RNA synthesis

The effects of polyinosinic, polycytidylic acid [poly(I) X poly(C)] on the activation and RNA metabolism in murine peritoneal macrophages (M phi) elicited by proteose-peptone (pM phi) was investigated. Poly(I) X poly(C) triggered the cytolytic activity of pM phi and augmented their glucose oxidation. In contrast, a profound depression of [3H]uridine incorporation into RNA was observed in poly(I) X poly(C)-activated pM phi. The degree of depression of RNA labeling paralleled the dose of poly(I) X poly(C) used to activate the pM phi and the expression of tumoricidal activity. This decrease in [3H]uridine incorporation into M phi RNA could not be accounted for by decreased permeability of the activated M phi to [3H]uridine, or by instability of the labeled RNA. Moreover, analysis of the specific activity of the intracellular uridine triphosphate (UTP) pool and studies on the labeling of M phi RNA with [32P] orthophosphate indicated that the decreased RNA labeling was not due to changes in the specific activity of UTP. We concluded that poly(I) X poly(C)-activated pM phi exhibit a depressed rate of RNA synthesis. We suggest that the rate of RNA synthesis may be investigated as a potential new indicator for M phi activation.

Alcohol dehydrogenase activity in rat kidney cortex stimulated by oestradiol

Sex differences in alcohol dehydrogenase activity, determined by the influence of oestrogen hormones, were found to exist in the rat kidney. Oestradiol, but neither testosterone nor progesterone, was shown to be a powerful stimulator of kidney alcohol dehydrogenase activity in rats, maximally 6- to 8-times over control values. The Michaelis-Menten constant for acetaldehyde of both non-stimulated and oestradiol-stimulated kidney alcohol dehydrogenases was found to be similar, 6.7 x 10(-5) M and 7.8 x 10(-5) M, respectively. Actinomycin D was shown to have an additive effect (superinduction) on the oestradiol-induced increase in kidney enzyme activity. The findings suggest the possibility of the higher contribution of kidneys in ethanol intake and ethanol hepatic disease.

Changes in in vivo rates of protein synthesis on free and membrane-bound polysomes in rat brain during the development of physical dependence on ethanol and after the withdrawal of ethanol

Administration of ethanol and nutrients to rats thrice daily by gavage for 3 days produced a linear increase in physical dependence during the first 3 days and a 2% increase in body weight. Rates of protein synthesis on free and membrane-bound polysomes in whole brain and in 7 brain regions, comprising the entire brain, were measured in vivo under pool expansion conditions with [3H]leucine at intervals during the development and decay of ethanol dependence. During dependence development there was a progressive decrease in the rate of protein synthesis on free polysomes, but this change was not significant (P less than 0.05) until the third day, and a decrease in the rate on membrane-bound polysomes after 3 days. The inhibition of protein synthesis is attributable to a decreased rate of polypeptide elongation. There was no change in brain weight, DNA content, ribosome content, ribosome distribution of mRNA pool size. There was, however, a decrease in leucine uptake after 3 days. In an attempt to distinguish between the acute effects of ethanol on regional rates of protein synthesis and those changes associated with dependence development, rates were measured 1.5 h after administering a 5 g/kg dose of ethanol to both control and dependent rats. Rates on free polysomes in the hippocampus-amygdala and thalamus-hypothalamus and on membrane-bound polysomes in the cerebellum and hippocampus-amygdala of dependent rats were reduced; however, there was a general reduction in the rates in control rats that may have obscured reductions in other regions from dependent rats. During early withdrawal, 12 h after the last dose of ethanol, there was an increase in the rate of free polysomes in the pons-medulla and striatum-septum and on membrane-bound polysomes in the hippocampus-amygdala, and a decrease in the rate on free polysomes in the cortex and thalamus-hypothalamus and on membrane-bound polysomes in the cortex. After 24 h, there was an increase in the rate on free polysomes in all regions (cerebellum, cortex, mesencephalon, striatum-septum and thalamus-hypothalamus) except the hippocampus-amygdala and pons-medulla and an increase in the rate on membrane-bound polysomes in all regions (cortex, hippocampus-amygdala, mesencephalon, pons-medulla and striatum-septum) except the cerebellum and thalamus-hypothalamus. The possible relationship of these changes to the homeostat hypothesis of ethanol dependence is discussed.

Effects of actinomycin D on dexamethasone induced hepatic glycogen accumulation: morphological and biochemical observations

Effects of inhibition of protein synthesis by actinomycin D (ACT) on the acute stimulation of hepatic gluconeogenesis and glucose-6-phosphatase (G6Pase) by the glucocorticoid, dexamethasone (DEX), in adrenalectomized (ADX) rats, were investigated using both morphological and biochemical means. Examination of ultra-thin sections of liver in the electron microscope revealed that ACT, administered alone or with DEX, resulted in a failure of hepatic glycogen accumulation to occur. Smooth endoplasmic reticulum (SER) appeared similar to that of the ADX-untreated animals, with occasional suggestions of increased amounts of membrane in ACT-treated animals. G6Pase activity in homogenates was increased, as was activation of the enzyme under all experimental conditions, when compared with ADX-untreated controls. The DEX-induced increase in G6Pase activity in SER failed to occur to any appreciable extent in ACT-treated animals. Plasma glucose levels increased slightly when ACT and DEX were present simultaneously. It is suggested that ACT countered the inductive effects of DEX on hepatic glycogen synthesis, but only partially suppressed acute stimulation of gluconeogenesis. A possible superinduction of G6Pase enzyme synthesis through increased efficiency of translation of extant mRNA is discussed. It is proposed that ACT inhibited the formation of appropriate SER membranes and/or other components necessary for glycogen accumulation.

Synthesis and secretion of uteroglobin in rabbit endometrial explants cultured in vitro

Explants from rabbit endometrium incorporate [35S] methionine into uteroglobin and other proteins in an essentially linear fashion for at least 8 h. Newly synthesized uteroglobin was characterized by gel chromatography, sodium dodecyl sulphate gel electrophoresis and immunological techniques. Labelled uteroglobin accumulates in the tissue explants during the first 3 h and then reaches a plateau level. Secretion of uteroglobin into the medium is detected after a 1-h lag period and proceeds linearly thereafter. Explants from animals treated with estradiol alone or estradiol plus progesterone (pseudopregnancy) synthesized respectively 2--3-fold and 10--20-fold more uteroglobin than explants from control animals. The rate of degradation of uteroglobin in the in vitro system was not affected by the hormonal treatment of the animals. There is a good correlation between the uteroglobin content in the uterine fluid and the rate of synthesis of uteroglobin in endometrial explants, suggesting that the in vitro system faithfully reflects the in vivo hormonal effects on uteroglobin synthesis.

Avidin induction by tissue injury and inflammation in male and female chickens

1. The occurrence and inducibility of the biotin-binding egg white protein (avidin) in the chicken is not restricted to the oviduct. 2. Inflammatory treatments (intestinal injury, actinomycin D) induced avidin in a number of tissues of young and adult hens and roosters, but not of female rats and mice. Highest avidin concentrations were found in the organs containing epithelial cells and serous membrane. 3. The expression of the avidin gene by tissue injury and inflammation suggests that avidin has a significant function in the injured and inflamed chicken tissues.

Nitrogen source regulates glutamine synthetase mRNA levels in Neurospora crassa

Neurospora crassa glutamine synthetase mRNA was measured by its capacity to direct the synthesis of the specific protein in a cell-free system derived from rabbit reticulocytes. N. crassa cultures grown on glutamate as the sole nitrogen source had higher mRNA activities than did those grown on glutamine. The differences were about 10-fold when polysomal RNA was used for translation and about 5-fold when either total cellular RNA or polyadenylic acid-enriched cellular RNA was used. These data indicate that in exponentially growing N. crassa, the nitrogen source regulates glutamine synthetase by adjusting specific mRNA levels.

The utilization of copper and its role in the biosynthesis of copper-containing proteins in the fungus, Dactylium dendroides

Aspects of the utilization of copper by the fungus, Dactylium dendroides, have been studied. The organism grows normally at copper levels below 10 nM. Cells grown in medium containing 30 nM copper or less concentrate exogenous metal at all levels of added copper; copper uptake is essentially complete within 15 min and is not inhibited by cycloheximide, dinitrophenol or cyanide. These results indicate that copper absorption is not an energy-dependent process. The relationship between fungal copper status and the activities of three copper-containing enzymes, galactose oxidase, and extracellular enzyme, the cytosolic, Cu/Zn superoxide dismutase and cytochrome oxidase, has also been established. The synthesis of galactose oxidase protein (holoenzyme plus apo-enzyme) is independent of copper concentration. Cells grown in copper-free medium (less than 10 nM copper) excrete normal amounts of galactose oxidase as an apoprotein. At medium copper levels below 5 micrometer, new cultures contain enough total copper to enable the limited number of cells to attain sufficient intracellular copper to support hologalactose oxidase production. As a result of cell division, however, the amount of copper available per cell drops to a threshold of approx. 10 ng/mg below which point only apogalactose oxidase is secreted. Above 5 micrometer medium copper, holoenzyme secretion is maintained throughout cell growth. The levels of the Cu/Zn superoxide dismutase respond differently in that the protein itself apparently is synthesized in only limited amounts in copper-depleted cells. Total cellular superoxide dismutase activity is maintained under such conditions by an increase in activity associated with the mitochondrial, CN(-)-insensitive, manganese form of this enzyme. Cells grown at 10 micrometer copper show 83% of their superoxide dismutase activity to be contributed by the Cu/Zn form compared to a 17% contribution to the total activity in cells grown at 30 nM copper, indicating that the biosynthesis of the Cu/Zn and Mn-containing enzymes is coordinated. The data show that the level of copper modulates the synthesis of the cytosolic superoxide dismutase. In contrast, the cytochrome oxidase activity of D. dendroides is independent of cellular copper levels obtainable. Thus, the data also suggest that these three enzymes utilize different cellular copper pools. As cells are depleted of copper by cell division, the available copper is used to maintain Cu/Zn superoxide dismutase and cytochrome oxidase activity; at very low levels of copper, only the latter activity is maintained. The induction of the manganisuperoxide dismutase in copper-depleted cells should have practical value in the isolation of this protein.

Induction of ovalbumin synthesis in immature chicks by actinomycin D and thioacetamide

Actinomycin D and thioacetamide induced ovalbumin synthesis and increased serum progesterone concentrations in immature chicks. The increase in progesterone induced by the carcinogens actinomycin D and thioacetamide may account for the induction of ovalbumin synthesis.

A change in the stability of globin mRNA during the induction of murine erythroleukemia cells

The stability of globin mRNA in murine erythroleukemia cells (Friend cells) before and during DMSO-induced differentiation was investigated. Cells were exposed to 3H-uridine for 2 hr and then transferred to medium without the radioactive precursor. The loss of radioactivity in total RNA, poly(A)-containing RNA and globin mRNA was followed. The globin mRNA was isolated using a highly specific globin cDNA column. In uninduced cells and cells early in differentiation, the globin mRNA decays with a half-life of less than 50 hr. After 4 days of induction, the globin mRNA decays with a half-life of 17 hr, demonstrating a change in stability during the induction process. Although the stability of globin mRNA changes during induction, this is not true for total poly(A)-containing RNA. At all times of induction, the poly(A)-containing RNA decays as two populations, one with a half-life of 6 hr and the other with a half-life of 36 hr. The half-life of the rRNA also remains unchanged during differentiation.

Postinductive actinomycin D effects on the concentrations of cadmium thionein, zinc thionein, and copper chelatin in rat liver

The time courses of induction in rat liver of copper chelatin by copper, cadmium thionein by cadmium, and zinc thionein by copper, cadmium, and zinc were monitorg metal were used in order to avoid toxic effects, being 5 mg zinc, 0.5 mg copper, and 0.25 mg cadmium per kg body weight. Peak times of induction and half times of decay observed were: copper chelatin (9 h, 8.6 h), cadmium thionein (18 h, 6.80 days), and zinc thionein (zinc rats, 18 h, 10.1 h; copper rats, 9 h, 18.2 h; cadmium rats, 24 h, 4.53 days). Administration of actinomycin D (1 mg per kg body weight) at the peak times of induction of the various proteins had no effect on the concentrations of chelatin or cadmium thionein observed up to 24 hours later, but in the case of zinc thionein, induced by zinc, copper, or cadmium, elevated concentrations were observed up to 23 h after administration of the drug. Such behavior is reminiscent of superinduction previously seen with other proteins and enzymes. We postulate that the intracellular concentration of free zinc in liver is of fundamental importance in the induction of zinc thionein, and this can be distributed by exogenous copper or cadmium resulting in the induction of synthesis of zinc thionein.

Progesterone receptors of chick oviduct

The chick oviduct progesterone receptor has been purified to homogeneity by affinity chromatography and its molecular action studied in vitro. The native receptor is a 200,000 MW dimer of two dissimilar 4S subunits with different intranuclear function. The receptors directly regulate RNA chain initiation sites in oviduct chromatin by interactions involving target tissue nuclear acceptor sites. There is a 1:1 correspondence between receptor "acceptor" sites and RNA sites. Only the dimer form of the receptor is active in vitro on chromatin templates. The study suggests a novel model for hormone action which can be tested directly in this system.

Stimulation of in vitro translation of messenger RNA by actinomycin D and cordycepin

Actinomycin D and cordycepin were tested for their effect on translation in the wheat germ embryo extract and reticulocyte lysate assays for in vitro protein synthesis. Both drugs were found to stimulate the incorporation of 35S-labeled methionine into protein up to threefold as compared to control assays. This was true for synthesis directed by murine myeloma polyadenylate-containing RNA, tobacco mosaic virus RNA, and endogenous reticulocyte messenger RNA.

Direct induction by estradiol on vitellogenin synthesis in organ cultures of male Xenopus laevis liver

Organ cultures of liver from untreated male Xenopus respond to 17 beta-estradiol in the culture medium by synthesizing and secreting the yolk protein precursor vitellogenin. Vitellogenin synthesis, as a primary response, is first detectable on the fourth day of culture, and comprises up to 12% of the protein synthesized on the eighth day. Estradiol is required during the lag period of 4 days. Tissue from male Xenopus injected with 1 mg of estradiol 30 days before the start of culture responds more rapidly and to a greater extent to estradiol in the medium than tissue from uninjected males. During such a secondary response, vitellogenin is first detectable in the medium on the second day of culture, and becomes up to 24% of the protein synthesized on day 6. The rate of amino acid incorporation into total protein also increases in response to estradiol, but the rate of synthesis of albumin decreases rapidly in culture whether or not estradiol is present, in both the primary and secondary responses. A maximal response is seen with 10(-8) M estradiol. Progesterone, testosterone, dexamethasone, and insulin neither induce vitellogenin synthesis in culture nor modify the response to estradiol. DNA synthesis inhibitors do not prevent the response to estradiol in vitro, suggesting that cell division is not required for the initial response leading to vitellogenin synthesis.