Separation of single-stranded ribonucleic acids by acrylamide-agarose-urea gel electrophoresis

Effects of Continuous Estradiol Administration by Polydimethylsiloxane and Paraffin Implants on Serum Hormone Levels and Uterine Responses

Since tonic elevated estrogen levels are associated with toxic responses, including tumor promotion, we investigated the effects of continuous estradiol (E2) administration by paraffin or polydimethylsiloxane (Silastic) implants on pituitary and uterine responses. Ovariectomized (OVEX) Sprague-Dawley rats implanted with low-dose (P1) or high-dose (P2) paraffin pellets showed initial high serum E2 levels that decayed rapidly. Silastic implants provided more constant pharmacological serum E2 levels during the 14 days of exposure. Rising serum LH and FSH levels in OVEX controls were suppressed by all E2 implants. Serum prolactin levels, low in OVEX controls, rose after implantation (P1 and P2) but decayed to control values by 14 days. Prolactin induced by pharmacological E2 levels initially rose, dropped by 72 hours, but again rose at later times. Uterine weight, low in OVEX controls, was increased by all implants. At later times, paraffin implants did not appear to release significant amounts of E2. However, removal of P2 implants from donors followed by transfer to new recipients stimulated uterine growth in recipients. All implants increased uterine DNA and RNA levels and the RNA/DNA ratio during the first 24–48 hours, followed by maintenance of elevated values. Poly(A)-containing RNA, isolated by oligo(dT) cellulose chromatography, comprised a constant percentage of RNA at all hormone levels and treatment times, suggesting a coupling of total RNA and poly(A)-containing RNA accumulation. Results are discussed in relation to the carcinogenic properties of estrogens, known to be correlated with continuous exposure to elevated estrogen levels.

Enrichment and analysis of RNA centered on ion pair reverse phase methodology

Here we describe a procedure for the rapid enrichment of RNA from cell extracts and the subsequent fractionation and analysis of the "small RNA" population by ion pair reverse phase chromatography. Solid phase extraction procedures have been developed utilizing nonporous alkylated poly(styrene-divinylbenzene) particles in conjunction with ion pair reagents to enrich total RNA. This approach facilitates the selective enrichment and separation of the relatively lower abundance small RNAs, from the more abundant higher molecular weight rRNA species. We also describe the application of monolithic capillaries in conjunction with ion pair reverse phase chromatography to bring increased sensitivity in the analysis of very low abundance RNAs. These approaches will simplify the biochemical analysis of this class of molecules, which are emerging as important regulators of global gene expression in higher organisms.

Denaturing RNA electrophoresis in TAE agarose gels

Current methods of analytical RNA electrophoresis are based on the utilization of either complicated laboratory instrumentation or toxic, carcinogenic, or expensive chemicals. We suggest here the use of classical Tris-acetate-ethylenediamine tetraacetic acid (TAE) agarose gels combined with prior denaturation of RNA samples in hot formamide for the electrophoretic separation of RNA species. We present a brief comparison of the proposed TAE/formamide method with the most common 3-(N-morpholino)propanesulfonic acid/formaldehyde agarose gel protocol and show that both methods produce comparable results for size determination of RNA molecules and subsequent Northern blotting of gels. In addition to purified RNA samples, the robustness of the TAE/formamide protocol is demonstrated by its suitability for the analysis of RNA quality in crude yeast cell lysates containing large amounts of proteins, DNA, and other contaminating molecules. We therefore propose the TAE/formamide agarose electrophoresis as a rapid, simple, and cheaper alternative to current methods of RNA electrophoresis. Additionally, another benefit is the reduced exposure of laboratory personnel to hazardous chemicals.

In vitro translation of tomato bushy stunt virus RNA

In vitro translation of tomato bushy stunt (TBSV)-RNA in a rabbit reticulocyte system resulted in synthesis of five proteins P 18, P 25, P 34, P 35, and P 40. The P 40 protein was identified as the viral coat protein. Fractionation of TBSV-RNA and subsequent translation provided evidence for the existence of discrete subgenomic RNAs.

Cap accessibility correlates with the initiation efficiency of alfalfa mosaic virus RNAs

The rate of cap removal from the alfalfa mosaic virus (A1MV) RNAs with tobacco acid pyrophosphatase (TAP) depends on the RNA species. At 37 degrees C and in the absence of divalent cation, RNA 3 reacts more slowly than the other three, which are decapped at similar rates. In the presence of magnesium, at 25 degrees C, TAP also discriminates against RNA 1. Thus the order of reactivity with TAP largely mimics the hierarchy of initiation efficiencies of the A1MV RNAs (Godefroy-Colburn et al., preceding paper in this journal). Our interpretation of these findings is that cap accessibility is what limits the rate of reaction with initiation factors as well as with TAP. In this hypothesis, translational discrimination between naturally capped messages would be related to the rate of 'breathing' of their 5' ends.

Translational discrimination between the four RNAs of alfalfa mosaic virus. A quantitative evaluation

In an attempt to relate the translational characteristics of alfalfa mosaic virus (A1MV) RNAs to their structure [Ravelonandro et al. (1983) Nucleic Acids Res. 11, 2815-2826; Gehrke et al. (1983) Biochemistry 22, 5157-5164] we measured the relative affinities (discrimination ratios) of these RNAs for the initiation complex, in the wheat germ extract and in the nuclease-treated reticulocyte lysate, using a competition method designed by Brendler et al. [(1981) J. Biol. Chem. 256, 11747-11754]. As a prerequisite of this study we ascertained that the molecular mass distribution of the translation products was independent of RNA concentration in both translation systems. In the wheat germ extract the discrimination ratios are very similar for two strains of A1MV (S and B) which differ mainly by the presence (strain S) or absence (strain B) of a stable 5'-proximal hairpin. Hence this structure has no bearing on discrimination. Taking the affinity of RNA 3 as reference, the following orders of magnitude are found for the affinities of the different RNAs in the wheat germ: RNA 3, 1.0; RNA 1, 10; RNA 2, 60; RNA 4, 150. In the reticulocyte lysate the discrimination ratios are not significantly different from the wheat germ. Thus it seems that the mechanism of discrimination is essentially the same in the two translation systems, despite a difference in rate-limitation.

Biosynthesis of pentosyl lipids by pea membranes

Pea membranes were incubated with UDP-[14C]xylose or UDP-[14C]arabinose and sequentially extracted with chloroform/methanol/water (10:10:3, by vol.) and sodium dodecyl sulphate (2%, w/v). An active epimerase in the membranes rapidly interconverted the two pentosyl nucleotides. Chromatographic analysis of the lipid extract revealed that both substrates gave rise to xylose- and arabinose-containing neutral lipids, xylolipid with properties similar to a polyisoprenol monophosphoryl derivative, and highly charged lipid-linked arabinosyl oligosaccharide. When UDP-[14C]pentose or the extracted lipid-linked [14C]arabinosyl oligosaccharide were used as substrates, their 14C was also incorporating into sodium dodecyl sulphate-soluble and -insoluble fractions as major end products. Polyacrylamide-gel electrophoresis of sodium dodecyl sulphate-soluble products indicated the formation of mobile components with Mr values between 40 000 and 200 000 (Sepharose CL-6B). The lipid-linked [14C]arabinosyl oligosaccharide possessed properties comparable with those of unsaturated polyisoprenyl pyrophosphoryl derivatives. It was hydrolysed by dilute acid to a charged product (apparent Mr 2300) that could be fractionated in alkali. It was degraded to shorter labelled oligosaccharides by slightly more concentrated acid and eventually to [14C]arabinose as the only labelled component. Susceptibility to acid hydrolysis, and methylation analysis, indicated that the oligosaccharide contained approximately seven sequential alpha-1,5-linked arabinofuranosyl units at the non-reducing end. Several acidic residues appear to be interposed between the terminal arabinosyl units and the charged lipid.

Evidence of proteolytic activation of Sendai virus in mouse lung

A device was made to analyze the pneumotropism of Sendai virus in mouse. Minced lung blocks were prepared from the mouse intranasally infected with Sendai virus for 2 hours and cultured in a CO2 incubator. This culture system provided a suitable in vitro model of Sendai virus infection in mice in terms of the distribution of the viral antigens and histopathological findings. The progeny virus recovered from the lung culture was already activated and was accompanied by the cleavage of F glycoprotein into F1 and F2. This fact demonstrates that the activating mechanism is reversed in the lung culture as found in vivo infection of mouse lung. The viral activation and the cleavage of F glycoprotein were simultaneously inhibited by tosyllysylchloromethylketone, leupeptin, soybean trypsin inhibitor and antipain, but not by tosylamidophenylethylchloromethyl-ketone, chymostatin, pepstatin, iodoacetamide, phenylmethylsulfonylfluoride and p-chloromercuribenzoate. These results show that the activating enzyme of Sendai virus found in the lung culture was similar to trypsin. The existence of the activating enzyme may support the replication of Sendai virus in mouse lung in multiple-step and also result in the lung pathology.

Poly(A) length, cytoplasmic adenylation and synthesis of poly(A)+ RNA in early mouse embryos

The poly(A) content of early mouse embryos fluctuates widely: after a transient increase in the one-cell embryo, there is a 70% drop in the two-cell and an approximately fivefold increase between the two-cell and early blastocyst stages (L. Pikó and K. B. Clegg, 1982, Dev. Biol. 89, 362-378). To shed light on the significance of these changes, we analyzed the size distribution of total poly(A) from embryos at different stages of development by gel electrophoresis and hybridization with [3H]poly(U). The number-average size of poly(A) tracts varies only slightly, from 61 to 77 nucleotides, indicating that the changes in poly(A) content are due primarily to changes in the number of poly(A) sequences, i.e., the number of poly(A)+ mRNA. From these data, the number of poly(A)+ mRNA can be estimated as follows: ovulated egg, 1.7 x 10(7); one-cell embryo, 2.4 x 10(7); late two-cell, 0.7 x 10(7); late eight-cell, 1.3 x 10(7); and early blastocyst, 3.4 x 10(7). These results suggest the elimination of the bulk of maternal poly(A)+ mRNA at the two-cell stage, to be replaced by newly synthesized mRNA derived from the embryonic genome. To study the synthesis of poly(A)+ mRNA, we cultured mouse embryos in vitro with [3H]adenosine and analyzed the labeled poly(A)+ RNA as to molecular size, length of the poly(A) tail, and relative distribution of label in poly(A) vs internal locations. We observed an active incorporation of label into large-molecular-weight (average size about 2 kb) poly(A)+ RNA at all stages from the one-cell to the blastocyst. However, in the one-cell embryo, about 70% of the label was localized in the poly(A) tail, suggesting cytoplasmic polyadenylation, and only about 30% was localized in the remainder of the molecule, suggesting the complete new synthesis of a small amount of poly(A)+ RNA. Differences in the size distribution of the labeled poly(A) as compared with the total poly(A) in the one-cell embryo indicate that the labeling is not due to a general turnover of poly(A) tails, but rather to the polyadenylation of previously nonpolyadenylated, stored RNA. Significant new synthesis of poly(A)+ RNA is evident from the two-cell stage onward and most likely accounts for the sharp rise in the number of poly(A)+ RNA molecules by the early blastocyst stage.

In vitro transcription of defective interfering particles of influenza virus produces polyadenylic acid-containing complementary RNAs

Influenza virus defective interfering (DI) RNAs, which originate from polymerase genes by simple internal deletion, can be transcribed in vitro. These DI RNA transcripts contain covalently linked polyadenylic acid, and their synthesis is dependent on ApG or capped RNAs as primers. Furthermore, like the standard viral RNA transcripts, they are complementary in nature and are slightly smaller in size compared with the corresponding DI RNAs. Hybridization of the specific DI RNA transcripts with the corresponding DI RNA segments and analysis of the duplex RNA by gel electrophoresis indicate that they are not incomplete polymerase gene transcripts, but rather the transcripts of the DI RNAs. Since influenza virus DI RNAs contain both the 5' and the 3' termini and transcribe polyadenylic acid-containing complementary RNAs in vitro the mechanism of interference may differ from that of the 5' DI RNAs of Sendai and vesicular stomatitis viruses.

Cloning the double-stranded RNA genes of reovirus: sequence of the cloned S2 gene

The genes of the Dearing strain of reovirus serotype 3, which consist of double-stranded RNA, have been cloned into pBR322 by tailing both strands of each gene with poly(A), transcribing them with reverse transcriptase, self-hybridizing the cognate plus and minus cDNA strands, incubating them with Escherichia coli DNA polymerase I to ensure that they are complete, and cloning the double-stranded cDNA molecules by standard procedures. The sequence of the cloned S2 gene has been determined. The sequence at the termini are exactly the same as those at the ends of the native double-stranded RNA gene. The gene is 1,329 nucleotides long and possesses a single long open reading frame that starts at the first initiation codon (residue 19) and extends for 331 codons, sufficient to encode a protein of the same size as the known S2 gene product, protein sigma 2, a major reovirus core component (Mr, 38,000). A second open reading frame of 85 codons, in a different phase, starts close to where the first ends. The protein translated from this reading frame is unknown.

Expression of the gene coding for the small subunit of ribulosebisphosphate carboxylase during differentiation of tobacco plant protoplasts

A hybridization probe was used to study the regulation of expression of the gene coding for the small subunit of ribulose 1,5-bisphosphate carboxylase, during functional differentiation of protoplasts. A library of cDNA from poly(A)-containing RNA extracted from specially treated tobacco leaves was constructed in the plasmid pBR322 by blunt-end ligation. This library was screened by colony hybridization with 32P-labelled cDNA prepared from mRNA coding for the precursor of the small subunit. A positive colony was identified containing recombinant plasmids with a nucleotide sequence homologous to this mRNA. These plasmids, bound to diazobenzyloxymethylated cellulose paper, were then used as a hybridization probe. The results showed unambiguously that the small subunit was not transcribed in protoplasts but was transcribed in undifferentiated white and chlorophyll-containing green callus cultures derived from protoplasts. The discrepancy between these results and those obtained with classical techniques is discussed.

Synthesis of (2'-5')oligoadenylate and activation of an endoribonuclease in interferon-treated HeLa cells infected with reovirus

Treatment with interferon protected HeLa cells from infection with reovirus. This virus apparently activated an antiviral mechanism that was detected by the presence of (2'-5')oligoadenylate [(2'-5')An] in intact cells. The (2'-5')An was previously shown to activate an endoribonuclease, RNase L. We measured (2'-5')An by a sensitive competition-binding assay in cells infected at different multiplicities and for different lengths of time. Nanomolar concentrations of (2'-5')An were detected in cells infected at a multiplicity of greater than 5 after 2 h of infection, the time at which the infecting virions were uncoated. The level of (2'-5')An increased up to 6 h postinfection but declined afterward. To establish whether viral mRNAs were cleaved by RNase L, we analyzed the RNA extracted from infected cells by a highly specific hybridization assay on Northern blots. Full-sized reovirus mRNAs were detected in control infected cells, but not in interferon-treated infected cells, at 6 h postinfection. At this time, a nuclease activity could be detected in these cells by demonstration of cleavage of rRNA, degradation of cellular mRNA, and polysome breakdown in the presence of emetine. Since this inhibitor freezes ribosomes, cleavage of mRNA between ribosomes could only be accounted for by an endonuclease, presumably RNase L.

Relationship between structure of the 5' noncoding region of viral mRNA and efficiency in the initiation step of protein synthesis in a eukaryotic system

To determine whether the rate of protein synthesis is controlled by the structure of mRNA near its 5' terminus, protein-synthesizing ability, especially in its initial stage, was compared among RNAs of plant viruses. Those viruses used here contain several definite pieces of single-stranded RNA. Each of these RNAs acts as a messenger. Cucumber mosaic virus (CMV) RNA 5 synthesizes a small amount of a protein, Mr 7000, in an in vitro protein-synthesizing system from wheat germ or reticulocyte. Brome mosaic virus (BMV) RNA 4 synthesizes a large amount of a coat protein under the same conditions. Both RNAs have the same 5'-cap structure and a short noncoding region (10 nucleotides in CMV RNA 5 and 9 in BMV RNA 4) between the 5' terminus and the initiation codon AUG. A sequence complementary to the 3' terminal of 18S ribosomal RNA is contained in BMV RNA 4 but is not apparent in CMV RNA 5. Formation of the initiation complex for protein synthesis by the 5'-terminal-labeled mRNA of cytoplasmic polyhedrosis virus was inhibited by the addition of unlabeled BMV RNA 4 whereas it was only slightly inhibited by unlabeled CMV RNA 5. BMV RNA 4, which has a sequence complementary to rRNA, can form the initiation complex more easily than CMV RNA5. It is concluded that an apparent complementary sequence in the 3' terminal of 18S rRNA in the 5' noncoding region of eukaryotic mRNA and the 5'-cap structure enhance the rate of initiation complex formation in protein synthesis.

Spontaneous variation and synthesis in the U3 region of the long terminal repeat of an avian retrovirus

Recombinant DNA clones of a viral clone of spleen necrosis virus, an avian retrovirus, were found to have long terminal repeats of different sizes. The variation was in the U3 region of the long terminal repeats, and any one clone had U3 of the same size in both long terminal repeats. The U3 regions in the 5' and 3' long terminal repeat were shown both to be derived from the 3' long terminal repeat of parental virus DNA.

Characterisation of viral RNA in cells infected with the murine coronavirus JHM

The murine coronavirus JHM induces in Sac(-) cells seven major and two minor RNA species. These RNAs are polyadenylated and single stranded. Their sizes were estimated by electrophoresis in agarose gels containing methylmercury hydroxide. The mol. wts. for the major species are 6.67 x 10(6) for RNA of genome size, 3.42 x 10(6) for RNA 2, 2.76 x 10(6) for RNA 3, 1.35 x 10(6) for RNA 4, 1.19 x 10(6) for RNA 5, 0.93 x 10(6) for RNA 6 and 0.62 x 10(6) for RNA 7. The minor species have a size of 4.7 x 10(6) (RNA a) and 1.5 x 10(6) (RNA b). No essential difference in the number and proportion of each RNA species was found between total cytoplasmic RNA, polyadenylated cytoplasmic RNA and RNA extracted from pelleted polysomes, nor was any difference found during the infection cycle. The major RNA species are likely to be subgenomic mRNAs.

Noncytopathic mutants of Newcastle disease virus are defective in virus-specific RNA synthesis

We have studied virus-specific RNA synthesis in cells infected by six noncytopathic (nc) mutants of the Australia-Victoria wild-type strain (AV-WT) of Newcastle disease virus (NDV) (19). The rates of NDV-specific RNA synthesis in mutant infection were three to sevenfold lower than those observed in wild-type infection. Velocity sedimentation of this NDV-specific RNA revealed that the lower rates of synthesis in mutant infection correlated with reduced accumulation of 18S and 35S mRNA. Electrophoresis in polyacrylamide-urea gels showed that accumulation of all of the 18S mRNA species was reduced and no new species could be detected. Primary transcription appeared unaltered in mutant infection. Cells infected with two naturally occurring avirulent strains of NDV also showed less accumulation of 18S mRNA. Electrophoresis of this RNA resulted in patterns which differed from those obtained with RNA from either AV-WT or nc mutant infection. Complementation for RNA accumulation between the nc mutants and RNA- temperature-sensitive mutants of AV-WT (32) suggested a common defect in the nc mutants. Analysis of plaque-forming revertants of five of the nc mutants revealed that viral RNA synthetic capacity, cell killing, and plaque-forming ability correlated absolutely. These results suggest that viral RNA synthesis and cytopathogenicity may be causally related. In addition, several of the plaque-forming (and cell-killing) revertants were found to be unable to induce fusion from within in infected cell cultures. This result, coupled with the finding that several of the nc mutants are capable of wild-type levels of fusion from within, suggests that the ability to cause such fusion does not correlate with the ability to kill cells.

Defective interfering influenza viruses and host cells: establishment and maintenance of persistent influenza virus infection in MDBK and HeLa cells

WSN (H0N1) influenza virus upon undiluted passages in different species of cells, namely, bovine kidney (MDBK), chicken embryo (CEF), and HeLa cells, produced a varying amount of defective interfering (DI) virus which correlated well with the ability of the species of cell to produce infectious virus. However, the nature of the influenza DI viral RNA produced from a single clonal stock was essentially identical in all three cells types, suggesting that these cells do not exert a great selective pressure in the amplification of specific DI viral RNAs either at early or late passages. DI viruses produced from one subtype (H0N1) could interfere with the replication of infectious viruses belonging to other subtypes (H1N1, H3N2). DI viral RNAs could also replicate with the helper function of other subtype viruses. The persistent infection of MDBK and HeLa cells could be initiated by coinfecting cells with both temperature-sensitive mutants (ts-) and DI influenza viruses. Persistently infected cultures cultures at early passages (up to passage 7) showed a cyclical pattern of cell lysis and virus production (crisis), whereas, at later passages (after passage 20), they produced little or no virus and were resistant to infection by homologous virus but not by heterologous virus. The majority of persistently infected cells, however, contained the complete viral genome since they expressed viral antigens and produced infectious centers. Selection of a slow-growing temperature-sensitive variant rather than the presence of DI virus or interferon appears to be critical in maintaining persistent influenza infection in these cells.

Incomplete influenza virus: partial functional complementation as revealed by hemadsorbing cell count test

In MDCK cells inoculated with an appropriate dilution of influenza virus, single hemadsorbing cells could be counted 8 h postinfection against a background of nonadsorbing cells. Standard virus preparation exhibited a linear relationship between the virus dilution and the number of hemadsorbing cells. With incomplete virus preparations obtained by passages of undiluted virus in chicken embryo, the dependence was nonlinear. A ts mutant (ts-29) of A/FPV/Weybridge (Hav1 Neq1) failed to convert MDCK cells into a hemadsorbing state at 42 degrees C. The ability of ts-29 to produce hemadsorbing cells could be rescued by incomplete wild-type virus. The capacity of incomplete virus for this partial functional complementation was inactivated by UV irradiation with one-hit kinetics. The size of the target was estimated to be 5.5 times smaller than that of the virus genome. The results suggest that at least some of the influenza virus genes in defective interfering particles are functional.

Recombination of human influenza A viruses in nature

In 1977, a unique event occurred in the epidemiology of influenza when a virus of the influenza A (H1N1) subtype, similar to a virus that had occurred in 1950, reappeared and caused worldwide epidemics but did not replace the prevailing influenza A (H2N2) subtype. Consequently, the two viruses co-circulated throughout the world and mixed infection of some individuals with both virus strains was detected, raising the possiblitity that recombination between the two strains might affect the future epidemiological behaviour of influenza. Serological analysis of virus isolates from influenza outbreaks during the winter of 1978-79, however, failed to detect any antigenic hybrids (H2N1 or H1N2). The investigation described here, was therefore, undertaken to detect recombinants among recent isolates of the H1N1 and H3N1 serotypes, involving genes coding for other than the surface proteins by RNA-RNA hybridisation. We report here the genetic characterisation of recombinants of both antigenic types.

Pathology of chickens infected with avian nephoblastoma virus MAV-2(N)

A neophroblastoma-inducing myeloblastosis-associated virus, MAV-2(N), derived from avian myeloblastosis virus was characterized with respect to biochemical composition and avian pathogenesis. Purified fibroblast-grown virus contained the same size 35S ribonucleic acid and the same relative amounts of viral polypeptides as another myeloblastosis-associated virus inducing predominantly osteopetrosis MAV-2(O). Plaque-purified MAV-2(N) induced a 76 to 93% incidence of nephroblastoma and a 3 to 50% incidence of osteopetrosis in SPAFAS and line 15 x 7 chickens: the oncogenic spectrum and the onset of nephroblastoma varied with the line of chicken and the route of injection. Renal neoplasms were manifest in chickens older than 2 months and grew to a massive size. Furthermore, 29% of control chickens housed with MAV-2(N)-infected chickens demonstrated nephroblastoma. MAV-2(N)-infected chickens had growth rates and blood packed cell volumes comparable to those of uninfected chickens. Infected chickens 2 months of age had increased kidney, liver, and spleen weights; tumor-bearing chickens 3 to 4 months of age had increased liver, lung, brain, pancreas, and bone weights. The concentration of albumin was decreased and the concentration of gamma globulin was increased in the serum of MAV-2(N)-INFECTED CHICKENS. Analysis of the sera of nephroblastoma-bearing chickens for virus and antibody showed that three states existed: (i) high levels of neutralizing antibody, (ii) high levels of virus, and (iii) simultaneous presence of both at low levels. The pathological and virological features of MAV-2(N) which distinguish it from MAV-2(O) are discussed.

Defect in polyamine metabolism in a BHK cell mutant temperature-sensitive for rRNA maturation

A mutant of BHK cells (ts422E) temperature-sensitive for processing 32S rRNA to 28S rRNA (Toniolo et al., '73) also loses the ability to synthesize polyamines and 5.8S rRNA when shifted to the non-permissive temperature (39 degrees). The activity of several enzymes not involved with polyamine synthesis, methylation of 32S rRNA, and small nuclear RNA production are apparently unaffected after at least 24 hours at 39 degrees. When cultures are returned to the permissive temperature (33 degrees), polyamine synthesizing capacity returns to normal as mature rRNA production resumes.

Transcription and translation of Newcastle disease virus mRNA's in vitro

Transcription directed in vitro by Triton-activated Newcastle disease virus (NDV) was stimulated and prolonged by the presence of cytoplasmic extracts of animal cells. The RNA products closely resembled those of NDV transcription in vivo by several criteria: binding to oligodeoxythymidylic acid-cellulose, the mobility and relative abundance of each major band resolved by polyacrylamide gel electrophoresis, and the ability to direct the accurate cell-free synthesis of polypeptides corresponding to the NDV proteins HN, F0/F1, NP, and M. Synthesis of a novel polypeptide related to NP but of higher apparent molecular weight was also detected. These results indicated that cell-free transcription under these conditions was a close facsimile of NDV transcription in vivo. In addition, both in vitro and in vivo, NDV polypeptides were synthesized in nonequimolar amounts which reflected the order of the genes in the transcriptional map: NP, F0, M, (47K, HN), L. Strains AV and HP, virulent strains which have differences in biological activities, exhibited differences in the polypeptides synthesized in infected cells and in cell-free systems.