Physico-chemical properties of interferon produced by a mixed leukocyte suspension

Physico-chemical properties of partially purified interferon produced by a mixed culture of human peripheral blood leukocytes following induction with double-stranded RNA extracted from f2 phage infected Escherichia coli were studied. Molecular heterogeneity of the interferon preparation was demonstrated by gel chromatography on a Sephadex G-100 column, disc electrophoresis in polyacrylamide gel and by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The first two methods revealed 5 peaks, the latter 7 peaks of interferon activity. There was no difference in the molecular nature of interferon produced by cultures exposed to the inducer for the whole period of incubation and that produced by cultures from which the inducer was removed after a short induction time.

Stimulation by inlfuenza virus RNA of 3H-phenylalanine incorporation in a cell-free system

Purified and unpurified cell-free systems prepared from the chorioallantoic membrane of embryonated eggs were tested for polypeptide synthesis in the presence and absence of influenza virus RNA. Both systems exhibited an endogenous messenger activity determining 3H-phenylalanine incorporation into polypeptides in the absence of virus RNA. However, addition of influenza virus RNA to the systems clearly stimulated amino acid incorporation into polypeptides, offering the possibility of studying some aspects of the viral protein biosynthesis mechanism.

Interferon, double-stranded RNA, and protein phosphorylation

We reported earlier that the addition of double-stranded RNA and ATP increases the endonuclease activity more in an extract of Ehrlich ascites tumor cells which have been treated with an interferon preparation than in a comparable extract from control cells. We report here that the addition of double-stranded RNA to an extract from Ehrlich ascites tumor cells which have been treated with an interferon preparation [or with the interferon inducer poly(I)-poly(C)] promotes the phosphorylation by [gamma-32P]ATP of at least two proteins: P1 (molecular weight of 64,000) and P2 (molecular weight of 37,000). Double-stranded RNA also promotes the phosphorylation of at least one (i.e., P1) of these two proteins in an extract from cells which have not been treated with interferon, but the extent of phosphorylation is much smaller. Double-stranded RNA which has been degraded by RNase III, or DNA, does not promote the phosphorylation.

Interferon-induced inhibition of protein synthesis in L-cell extracts: an ATP-dependent step in the activation of an inhibitor by double-stranded RNA

The translation of encephalomyocarditis virion RNA in extracts from interferon-treated L-cells is inhibited by the addition of double-stranded RNA (dsRNA) at 400 ng/ml. A similar inhibition in response to dsRNA is seen in control cell extracts supplemented with small amounts of a postribosomal supernatant fraction from interferon-treated cells (interferon cell sap): Neither interferon cell sap nor dsRNA alone is inhibitory in control systems. The inhibition is much reduced if translation is carried out at low ATP concentrations.Conversely, the inhibitory capacity of the interferon cell sap is increased 100-fold if it is preincubated with dsRNA and ATP prior to its addition to the protein-synthesizing system. After this preincubation all detectable dsRNA can be removed without any diminution of the inhibitory activity of the cell sap. These results are compatible with a two-step model for the inhibition in which a pre-inhibitor is activated by dsRNA, the activated inhibitor then interacting with the protein synthesis system to inhibit translation.

Inhibition of protein synthesis in reticulocyte lysates by poliovirus

Addition of 1 X 10(10) p.f.u. purified poliovirus to 100 mul of a rabbit reticulocyte lysate protein synthesizing system causes a complete inhibition of initiation of protein synthesis. This inhibition is not due to the viral RNA nor to any contaminants of the preparation, but is most likely caused by the viral coat protein.

Variable response of normal and transformed mouse cells to interferon inducers

Balb/3T3 mouse cells, normal and SV40-transformed, produced interferon when induced with Newcastle disease and influenza viruses; transformed cells failed to respond to double-stranded RNA inducers.

Viral factors required for interferon induction by Newcastle disease virus in mouse macrophages and chicken embryo cells

The triggering mechanism for interferon synthesis in mouse peritoneal macrophages and chick embryo (CE) cells by Newcastle disease virus (NDV) exposed to hydroxylamine or homologous antiserum was investigated in relation to the intracellular fate of these agents. Inactivation of NDV at 22 degrees C by I M-hydroxylamine proceeded with first-order kinetics, whereas the interferon-inducing capacity of hydroxylamine-treated virus in macrophages was unimpaired. In contrast to infective NDV, hydroxylamine-inactivated virus produced interferon in CE cells, and such a virus still had partial RNA-dependent RNA polymerase activity. Hydroxylamine-inactivated NDV was adsorbed to and uncoated in both normal and chloroquine diphosphate treated cells, but no viral double-stranded RNA was detected. Hydroxylamine treatment of virion-extracted RNA and neutralization of intact virions by antibody abolished the capacity of the virus to induce interferon. Infective as well as neutralized NDV interacted with macrophages to the same degree, but association between NDV and CE cells was prevented by antibody-coating. In macrophages, the RNA of neutralized NDV became more sensitive to RNase than RNA of infective NDV, but this process was inhibited in chloroquine diphosphate-treated cells. These results suggest that interferon induction by NDV involves components of the virion which are present up to the regular uncoating process.

Further studies on the adjuvant effect of an interferon inducer (BRL 5907) on Newcastle disease and avian influenza inactivated vaccines

Vaccination of fowls with inactivated Newcastle disease (ND) virus and avian influenza (AI) virus oil emulsion vaccines containing an interferon inducer (BRL 5907) produced an enhanced immunological response. The Newcastle disease vaccine containing BRL 5907 induced earlier protection to challenge than Newcastle disease vaccine by itself and also produced an increase immune response when administered to day-old maternally immune and susceptible chicks.

[Analysis of cultures infected by vaccinal strains of viruses for detecting in them the integrated genome of these viruses (author's transl)]

White mice of 10-12 g were immunized with one of the three virus vaccines (vaccines against poliomyelitis, measles, smallpox) at various intervals. Poliovirus type II and measles virus, Edmonston strain, were labeled in tissue culture with 3H-uridine (30/uCi/ml). Smallpox virus (rabbit strain) was labeled with 3H-thymidine (30/uCi per ml) also in tissue culture. After purification and concentration of labeled poliomyelitis and measles viruses, viral RNA was isolated by double extraction with phenol, and precipitation with alcohol to which a yeast RNA-carrier was added. Isolation of 3H-thymidine-labeled viral RNA from smallpox virus was carried out by the same method with the addition of SDS to the final concentration of 1%. From the brain and lung cells of the vaccinated animals DNA was extracted by the kinetic reassociation method and hybridized with labeled viral nucleic acids. The formation of a hybrid with DNA-containing vaccine virus was controlled by chromatography in hydroxylapatite. No integration of viral and cell nucleic acids was demonstrated in our experiments, however, it cannot be ruled out completely, because this method does not detect homologous sequences if they occur in a small number of cells tested.

Translation of silk fibroin messenger RNA in an Ehrlich ascites cell-free extract

RNA identified by its base composition and T1 RNase oligonucleotide pattern as the message for silk fibroin was purified from mature posterior silk glands of Bombyx mori larvae and used to direct polypeptide synthesis in an Ehrlich ascites cell-free extract. Fibroin mRNA stimulated [3-H]alanine incorporation about 3- to 4-fold in the presence of 80 mM K+ and 4 mM Mg-2+. The stimulation was reduced in the presence of 5 times 10-minus 6 to 10-minus 4 M aurintricarboxylic acid, an inhibitor of the initiation of protein synthesis. The cell-free products were heterogeneous in size, including peptides as large as 100,000 daltons. They co-precipitated with carrier fibroin sequences after digestion with trypsin. A large fraction of the polypeptides synthesized in response to fibroin mRNA was precipitated by antiserum directed against amino acid sequences in noncrystalline region polypeptides of fibroin. Furthermore, after digestion with chymotrypsin, a major fraction of the cell-free products specifically co-precipitated with crystalline region sequences of native fibroin. The size and amino acid composition of the fibroin crystalline region polypeptides isolated from the cell-free products were similar to those from native fibroin.

Ability of tryptophan tRNA to hybridize with 35S RNA of avian myeloblastosis virus and to prime reverse transcription in vitro

Selected species of 4S RNA of chick embryo cells will hybridize in vitro with 35S RNA of avian myeloblastosis virus. A major tRNA component of the hybridizable 4S RNA is tryptophan tRNA. A hybrid prepared from purified tryptophan tRAN and 35S RNA of avian myeloblastosis virus in vitro is an efficient templateprimer for DNA synthesis catalyzed by reverse transcriptase (RNA-dependent DNA polymerase).

The characteristics of inhibition of protein synthesis by double-stranded ribonucleic acid in reticulocyte lysates

All types of double-stranded RNA (DSRNA) tested inhibit protein synthesis in rabbit reticulocyte lysates. The inhibition is characterized by its strongly biphasic kinetics, and can be enhanced by preincubation of the lysate with dsRNA in the absence of protein synthesis. Only properly and extensively matched dsRNA (greater than about 50 base pairs) has this property; no form of DNA, single-stranded RNA or even RNA-DNA hybrids act as inhibitors in this way. The cause of the inhibition appears to be a failure of initiator tRNA to associate with native ribosomal subunits in the initiation process (Darnbrough, C., Hunt, T., and Jackson, R. J. (1973) Biochem. Biophys. Res. Commun. 48, 1556-1564). We have shown that this block is not accompanied by stable association of dsRNA with the ribosomes. There are several reasons to believe that the mechanism of action of dsRNA may be complex with the possible involvement of at least one catalytic step. First, the lysate is inhibited by levels of dsRNA at which ribosomes are present in 100-fold excess over base pairs of dsRNA present. Second, high concentrations of dsRNA (greater than 10 mug per ml) are not inhibitory, but can in some, but not all experiments, reverse the inhibition caused by lower levels of dsRNA. Third, a lysate which has been inhibited by dsRNA, when mixed with a fresh lysate will inhibit synthesis in the mixture much more severely than would be expected from the concentration of dsRNA now present. These results indicate that low levels of dsRNA promote the formation of an inhibitor which may exist in two forms: one that is reversible by high levels of dsRNA and one that is irreversible.

Effect of chemically modified 70S RNA from avian myeloblastosis virus (AMV) upon the activity of AMV DNA polymerase

Adenine residues of 70S avian myeloblastosis virus (AMV) RNA are modified when reacted with chloroacetaldehyde. This modification introduces characteristic fluorescent epsilon-adenosine (epsilonA) probes which were used to monitor the reaction. Under suitable conditions, modified 70S(epsilonA) RNA was maintained intact and was inactive as a template for the AMV DNA polymerase. Furthermore, it inhibited the reaction catalyzed by AMV polymerase when 70S RNA was used as template-primer and had no effect on the two tested bacterial polymerases. Protection against the 70S (epsilonA) RNA inhibition was observed when 70S RNA was primed with oligo(dT) indicating preference of the polymerase for the oligo(dT) primed regions.