In vitro translation of polyadenylated RNA isolated from control and interferon-treated human promyelocytic HL-60 leukemic cells

Polyadenylated RNA has been isolated from control and interferon-treated HL-60 cells by centrifugation through cesium chloride and oligo(dT)-cellulose column chromatography. The affinity column-purified RNA is poorly translated in the mRNA-dependent rabbit reticulocyte lysates but is an excellent template for in vitro protein synthesis using the wheat germ cell extracts. The discrepancy in the efficiency of HL-60 mRNA utilization in the two commonly used cell-free protein synthesizing systems is attributable to an inhibitory component present in the polyadenylated RNA. This contaminant is most likely double-stranded RNA based on (i) the ability of 2-aminopurine (3-5 mM) or high concentrations of penicillium chrysogenum double-stranded RNA (10-15 micrograms/ml) to overcome the inhibition exerted by the component, and (ii) the ability of the component to promote the enzymatic conversion of ATP into 2-5A by the highly purified rabbit reticulocyte 2-5A synthetase.

Ontogeny of ppp(A2'p)nA-binding protein in mouse brain

Mouse brain tissue extracts at various stages of development show a drastic change in the specific activity of pp(A2'p)3A-[32P]pCp binding protein. Identification of the ppp(A2'p)3A-[32P]pCp binding protein was established by (i) binding to the specific ligand ppp(A2'p)3A-[32P]pCp, (ii) displacement of binding by nanomolar concentrations of pppA(pA)3, and (iii) affinity labeling techniques in which periodate oxidized ppp(A2'p)3A-[32P]pC was specifically cross-linked to a protein with a molecular weight of 85000. These data suggest that the ppp(A2'p)3A-[32P]pCp protein is closely associated with the process of cellular proliferation and differentiation.

Effect of temperature on ppp(A2'p)nA binding protein activities in rabbit reticulocyte lysates and other mammalian extracts

Lysates of rabbit reticulocytes and other mammalian cells are known to contain an activity which binds with high specificity ppp(A2'p)3A,3'-[32P]pCp. The binding activity shows a marked dependence on preincubation of lysates at different temperatures (4 degrees C - 45 degrees C). For example, binding was increased 50% by preincubation of rabbit reticulocyte lysates at 37 degrees C for 60 minutes. An identical preincubation of mouse brain extracts results in a greater than 90% loss of binding activity. Fractionation of rabbit reticulocyte lysates into the postribosomal supernatant (PRS) and the ribosomal salt wash (RSW), followed by heparin-agarose column chromatography, showed that with the PRS fraction, most of the binding activity is eluted with 600 mM KCl. With the RSW fraction, more than 50% of the binding activity is eluted with 250 mM KCl. These data suggest that multiple ppp(A2'p)nA binding protein activities exist in mammalian cells.

Induction of (2'-5')An-dependent endoribonuclease activity by interferon in cultured guinea pig macrophages

By a radiobinding assay, an affinity labeling technique, and a column procedure which quantitates mRNA intactness, evidence is presented on the induction of the (2'-5')An-dependent endoribonuclease by interferon in cultured guinea pig macrophages.

Double-stranded RNA-stimulated enzyme activities isolated from human placental extracts

A (2'-5')An synthetase activity was isolated from human placental extracts by affinity chromatography on poly(rI) . poly(rC)-agarose. The oligonucleotide (2'-5')An was identified by (1) chromatography on PEI-cellulose and DEAE-cellulose, (2) inhibition of polypeptide synthesis in lysed rabbit reticulocytes (3) competition of the binding of pppA(pA)3,3'-[32P]pCp to rabbit reticulocyte lysates, and (4) alkaline phosphatase digestion. The synthetase activity in most placental preparations is activated by natural or synthetic dsRNA. However, in a few placental synthetase preparations, dsRNA is only marginally stimulatory and only becomes effective by prior treatment of the enzyme preparations with the calcium-dependent micrococcal nuclease. This suggests that there is an endogenous placental dsRNA contaminant in the enzyme preparations. In some synthetase preparations, a second dsRNA-stimulated product, tentatively identified as the nucleotide 5'-IMP, is also observed. Because the specific AMP deaminase inhibitor coformycin (10 microM) blocks the formation of IMP from ATP and causes a quantitative accumulation of AMP, and because the formation of IMp becomes independent of dsRNA when ADP or AMP is used in place of ATP, the presence of a dsRNA-stimulated ATP phosphohydrolase (ATPase) activity in human placenta is suggested.

Some properties of a partially purified inhibitor(s) of protein synthesis from rat-liver mitochondria

We have previously described an inactive inhibitor of protein synthesis from rat liver mitochondria and its activation by brief incubation with N-ethylmaleimide [Wu, J. M. and Ibrahim, N.G. (1980) FEBS Lett. 119, 25-28]. To study the mode of action of the mitochondrial translational inhibitor (MTI), the relative distribution of monosomes and polysomes in rabbit reticulocyte lysates has been analysed by sucrose gradient centrifugation. These studies show that MTI causes a significant decrease in the amount of polysomes with marginal effect on the polysome profile. Under identical experimental conditions, addition of partially purified heme-regulated inhibitor results in a complete disaggregation of polysomes. Studies with micrococcal-nuclease-treated rabbit reticulocyte lysates suggest that the primary target of MTI is the inactivation of globin mRNA with relatively little effect on other components of the translational machinery. The inhibitor also degrades poly(U), vesicular stomatis virus mRNA, reovirus mRNA, but appears to be inactive against poly(A), Escherichia coli 16S rRNA, HeLa cell rRNA or chick embryo DNA. Chromatography of MTI on heparin-agarose results in the resolution of at least two inhibitory activities. The first inhibitory activity (eluted with 250 mM KCl) can be reversed (50-70%) with high concentrations of glucose 6-phosphate or MgGTP (0.7 mM or 3.3 mM) whereas the second inhibitory activity can only be partially reversed with poly(A)-rich RNA.

Hemifacial spasm: results of microvascular relocation

Twenty patients with hemifacial spasm were treated between February 1980 and June 1981. All presented with typical disabling unilateral contractions of the face. Computerized Tomographic Scan and angiograms ruled out structural mass lesions. All patients underwent posterior fossa microsurgical relocation of a vessel from the root entry zone of the facial nerve. An offending arterial loop was found in each case. Nineteen patients are free of symptoms and the remaining one is improved. One patient has permanent loss of hearing and two developed mild facial weakness. There has been no recurrence in 18 months follow up. These results given further support to the theory that hemifacial spasm is an affliction of the seventh nerve in the cerebello-pontine angle, most commonly caused by vascular cross compression at the root entry zone. Surgical relocation of the offending vessel relieves the symptoms and there appears to be no recurrence. This procedure is not difficult and carries acceptable risk for the patient with this disabling condition.

Synthesis and function of (2'-5')An: inhibition of (2'-5')An synthetase by heparin and the use of heparin-agarose for partial purification of (2'-5')An synthetase from rabbit reticulocyte lysates

Heparin, but not a number of other acid mucopolysaccharides, inhibits (2'-5')An synthetase partially purified from rabbit reticulocytes. The effect of heparin was apparent at 10 micrograms/ml (21%). Maximum inhibition was observed at 200 micrograms/ml (80%). At the latter concentration, the dsRNA-dependent (2'-5')An synthetase activity was inhibited 80% whereas the dsRNA-independent enzyme activity was inhibited only 30%. The formation of the dimer, trimer, tetramer and high oligomers of (2'-5')An was inhibited to the same extent with the addition of heparin. Heparin covalently bound to agarose beads was shown to be a useful affinity resin for the purification of (2'-5')An synthetase from rabbit reticulocyte lysates.

Evidence for cAMP-independent inhibition of S-phase DNA synthesis by prostaglandins

Two prostaglandins, prostaglandin E1 (PGE1) and prostaglandin B1 (PGB1), block S-phase DNA synthesis in synchronous cultured baby hamster kidney (BHK) cells. The prostaglandin inhibition of DNA synthesis does not appear to require elevated levels of cAMP. In BHK-21 cells that have been "desensitized" to prostaglandin stimulation of adenylate cyclase and, therefore, have control levels of cAMP, PGE1 retains its inhibitory effect on the incorporation of tritiated thymidine into DNA. When BHK cells are exposed to PGB1 (a prostaglandin that does not elicit a cAMP response), DNA synthesis is also blocked. In nonsynchronous cells exposed for 1 h to PGE and then incubated for 1 h with PGE removed, a rebound of DNA synthesis occurs, therefore providing evidence that a transient rise of cAMP in itself is not capable of causing a cascade of reactions that block the synthesis of DNA. In addition, the concentration of PGE required for inhibition of DNA synthesis is significantly less than that required for cAMP generation. Addition of 1 x 10(-8) M PGE to BHK cells can be shown to significantly inhibit DNA synthesis within 30 min, with half-maximal inhibition seen at 3 x 10(-7) M PGE. Cyclic AMP levels for controls were 4.9 +/- 0.2 and 4.6 +/- 0.1 for 1 x 10(-6) M PGE1. These findings suggest that the prostaglandins can act independently of cAMP at physiological concentrations; and, therefore, it is possible that prostaglandins have a physiological role in the control of cell growth during S-phase.

Increased erythropoiesis and 2'5'-A polymerase activity in the marrow and spleen of phenylhydrazine-injected rats

The rate of CFUE production in adult rats varies considerably according to whether the animals are rendered anemic by short or long term treatment with phenylhydrazine. The bone marrow responds during 2 months of phenylhydrazine injections with a progressive increase in CFUE, the spleen shows a rapid and larger rise after 3 daily injections followed by a decline to near zero, control numbers, after prolonged administration of the drug, and the liver never develops erythropoietic activity. Endogenous colonies, that is, colonies that grow in plasma clots without added erythropoietin, are most numerous in bone marrow after phenylhydrazine treatment, are always few in the spleen and are never present in cultures of liver cells. In both marrow and spleen, there is a direct correlation between the rate of erythropoiesis and 2'5'-A polymerase activity. These findings suggest that production of the enzyme may be an early event in erythroid cell differentiation.

The influence of reserpine on nitrogen metabolizing enzymes in chick liver

Reserpine, a Rauwolfia alkaloid, was shown to increase activity of the hepatic nitrogen metabolizing enzymes xanthine dehydrogenase, purine nucleoside phosphorylase, and tyrosine aminotransferase, when administered orally to young chicks. Using immunochemical techniques, this increase in xanthine dehydrogenase was shown to result from an enhanced de novo enzyme synthesis. The response pattern of the three enzymes to reserpine follows the same pattern to induction by high dietary protein suggesting that a common mode of action may be involved in the regulation of these enzymes. Alpha-Adrenergic blockers, phentolamine and phenoxybenzamine, effectively prevented the increased enzyme activities caused by administration of reserpine.

Core (2'-5')oligoadenylate and the cordycepin analog: inhibitors of Epstein--Barr virus-induced transformation of human lymphocytes in the absence of interferon

The 3'-deoxyadenosine (cordycepin) analog of (2'-5')oligo(A) [(2'-5')oligoadenylate with a triphosphate at the 5' end], synthesized enzymatically from cordycepin 5'-triphosphate in lysed rabbit reticulocytes or L-cell extracts was (i) inhibitory to translation in lysed rabbit reticulocytes and (ii) metabolically stable in extracts of either L cells or C85-5C lymphoblasts. The 5' dephosphorylated (core) (2'-5')oligo(A) and the core cordycepin analog can replace human fibroblast interferon in preventing the transformation of human lymphocytes after infection with Epstein--Barr virus B95-8 (EBV) as determined by the decreased incorporation of [3H]thymidine into cellular DNA and the inhibition of morphological transformation of EBV-infected lymphocytes. Whereas the naturally occurring core (2'-5')oligo(A) was cytotoxic to uninfected lymphocytes and proliferating lymphoblasts, the core cordycepin analog was not. Human leukocyte interferon was more effective than human fibroblast interferon in the inhibition of EBV-induced transformation of human umbilical cord lymphocytes and adult peripheral blood lymphocytes.

Control of protein synthesis in rabbit reticulocytes. Inhibition of polypeptide synthesis by ethanol

Ethanol (0.21-0.84 M) added to rabbit reticulocyte lysates results in a 42-89% decrease of polypeptide synthesis following a 60-min incubation at 30 degrees C. The onset of inhibition is preceded by a 5-15-min lag. Eukaryotic initiation factor 3 (eIF-2) (85% pure, 0.42-4.2 micrograms added/30-microliters assay) or high concentrations of cAMP, MgGTP, and glucose 6-phosphate (0.55-5.0 mM) partially reverse the inhibition was observed with fructose 6-phosphate (0.55 mM). Ethanol was also shown to directly inhibit ternary complex formation between eIF-2, GTP, and initiator Met-tRNA (50% inhibition with 0.5 M ethanol). The inhibitory effect of ethanol on polypeptide synthesis, however, appears to be independent of its effect on ternary complex formation, and may be related to the activation of a translational inhibitor. This tentative conclusions is based on the following results. First, when the postribosomal supernatant or unfractionated lysate is incubated with ethanol, the supernatant or lysate becomes inhibitory to polypeptide synthesis following a 60-min incubation with ethanol at 30 degrees C. Second, when ethanol-treated postribosomal supernatant is chromatographed on DEAE-cellulose, an inhibitory activity is observed. The peak of inhibition coincides with the elution position of a translational inhibitor termed heme-controlled repressor. Third, pro-heme-controlled repressor becomes more inhibitory to protein synthesis when incubated with ethanol. These findings suggest that ethanol may activate a translational inhibitor by affecting the proper conformational change of a dormant inhibitor.