THE REPLICATION OF BACTERIOPHAGE MS2. IV. RNA COMPONENTS SPECIFICALLY ASSOCIATED WITH INFECTION

Effect of virus infection on the stability and synthesis of actinomycin-resistant ribonucleic acid in baby-hamster kidney cells

1. The sucrose-gradient pattern of (32)P-labelled RNA synthesized in actinomycintreated baby-hamster kidney cells infected with foot-and-mouth-disease virus depends greatly on the period of labelling. 2. Fractions are formed in infected cells that sediment at 12-20s and have the same base composition as similar fractions found in non-infected cells that have been treated with actinomycin. 3. In the presence of guanidine, which completely inhibits viral RNA synthesis, these fractions are labelled to a greater extent than in non-infected cells.

Preparation and properties of a new DNase from Aspergillus oryzae

A DNase present in commercial preparations of Aspergillus oryzae alpha-amylase was purified 1550-fold in 25% yield by acetone precipitation and by chromatography on diethylaminoethyl- and carboxymethylcellulose. The enzyme was isolated free of contaminating RNases and DNases. The molecular weight of the enzyme determined by gel filtration on Sephadex G-100 was 48 000, while a molecular weight of 58 000 was determined for the single band observed upon polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The isoelectric point of the DNase is 9.2. The enzyme hydrolyzed only DNA with a pH optimum of 8.2 and was activated by Co2+, and to a lesser extent by Mg2+ and Mn2+. Native DNA was a better substrate than heat-denatured DNA. Enzymatic digests of calf thymus and E. coli DNA yielded oligomers of chain lengths ranging from 10 to 200, with mono- and small oligonucleotides (chain length less than 5) detected only when large (100 mg) amounts of DNA were fractionated by column chromatography on diethylaminoethyl-Sephadex A-25 in 7 M urea. The digestion products contained 5'-terminal phosphate groups and mostly adenosine at the 3' and guanosine and adenosine at the 5' ends.

Complexity of the structure of particles containing heterogeneous nuclear RNA as demonstrated by ribonuclease treatment

Brain ribonucleoprotein particles containing heterogeneous nuclear RNA (hnRNA) and a large number of polypeptides ranging from 23000 to 150000 molecular weight were treated with pancreatic and T1 ribonucleases at low (0.1 or 0.5 microng plus 5 or 25 units/ml), high (2 microng plus 100 units/ml) and very high (20 microng plus 1000 units/ml) concentrations. At low enzyme concentration, a large fraction of the particle material accumulated at 35-45 S. The accumulation was more marked for proteins in the 30000-38000 molecular weight range. Heterogeneous complexes containing a large spectrum of proteins with a characteristic distribution were disclosed between 60 and 200 S. At high ribonuclease concentration the total quantity of proteins at 35-45 S decreased, but the proteins of 30000-38000 molecular weight predominated. Heterogeneous complexes were also present. Finally at very high enzyme concentration, the particles were almost entirely hydrolyzed. Only a small amount of heterogeneous complexes subsisted at 30-190 S. The RNA content of the remaining ribonucleoprotein complexes as well as its size decreased upon ribonuclease treatment as shown by CsCl density determination and electrophoretic analysis. The results suggested that the stability of the complexes depended upon protein-protein as well as RNA-protein interactions. They also showed that sequences up to 200-300 nucleotides were protected by proteins against ribonuclease. The results were compatible with the existence of at least 3 constituents in the particles. The previously defined monoparticle population accumulating at 35-45 S was heterogeneous in respect to ribonuclease sensitivity and protein composition. The 30000-38000 molecular weight proteins accumulating at low ribonuclease and predominating afterwards were assumed to belong to monoparticles alpha. Monoparticles beta contained a larger range of proteins more easily released by the enzymes. The heterogeneous complexes were a third constituent whose relationship with the monoparticles war not established yet. A large fraction of the particle phosphoproteins was associated to these complexes. On the basis of our experiments in vitro it is assumed that monoparticle alpha can be preferentially isolated from the nuclei under conditions where endogeneous ribonuclease is high and (or) not inhibited. This might explain why, in certain cases, only one or a few proteins were described in nuclear particles instead of the complete set present in the native particles.

The binding of poly(rA) and poly(rU) to denatured DNA. I. Model studies with homopolymers

We have compared the properties of the poly(rA).oligo(dT) complex with those of the poly(rU).oligo(dA)n complex. Three main differences were found. First, poly(rA) and oligo(dT)n do not form a complex in concentrations of CsCl exceeding 2 M because the poly(rA) is insoluble in high salt. If the complex is made in low salt, it is destabilized if the CsCl concentration is raised. Complexes between poly(rU) and oligo(dA)n, on the other hand, can be formed in CsCl concentrations up to 6.6 M. Second, complexes between poly(rA) and oligo(dT)n are more rapidly destabilized with decreasing chain length than complexes between poly(rU) and oligo(dA)n. Third, the density of the complex between poly(rA) and poly(dT) in CsCl is slightly lower than that of poly(dT), whereas the density of the complex between poly(rU) and poly(dA) in CsCl is at least 300 g/cm3 higher than that of poly(dA). These results explain why denatured natural DNAs that bind poly(rU) in a CsCl gradient usually do not bind poly(rA).

Guanidinium-CsCl density gradients for isopycnic analysis of nucleic acids

The addition of guanidinium chloride to CsCl gradients lowers the apparent density of RNA, DNA, and hybrid polymers in such a way that all three can be banded, fractionated, and analyzed in one gradient with essentially no damage to their chemical integrity or to their biological activity.

Nucleic acid of rubella virus and its replication in hamster kidney cells

Ribonucleic acid (RNA) has been isolated from partially purified rubella virus preparations and fractionated by rate zonal centrifugation in sucrose density gradients. The bulk of the RNA sedimented as a sharp band with a sedimentation coefficient of 38S. Rubella virus RNA appears to be single-stranded on the basis of its sensitivity to the degrading action of ribonuclease. Fractionation by precipitation with 1 m NaCl, followed by chromatography on cellulose columns, and by rate zonal centrifugation in sucrose density gradients of labeled RNA isolated from actinomycin D-treated and infected baby hamster kidney cells revealed the presence of the following virus-specific types of RNA: (i) single-stranded RNA with a heterogeneous sedimentation pattern, the 38S viral RNA becoming the predominant species only after long periods of labeling late after infection; (ii) double-stranded RNA with a sedimentation coefficient of 20S; (iii) RNA apparently composed of 20S double-stranded RNA and single-stranded branches. On the basis of their properties, the last two species were tentatively identified as the replicative form and the replicative intermediate of rubella virus RNA. Rubella virus RNA was infectious.

Characterization of influenza virus ribonucleic acid duplex produced by annealing in vitro

A ribonuclease-resistant ribonucleic acid (RNA) with a sedimentation coefficient of 12S was obtained by self-annealing influenza virus-specific RNA isolated from infected cells. It had the properties of double-stranded RNA. (i) Sedimentation behavior in sucrose gradient was independent of salt concentration. (ii) Thermal transition profile was sharp; the melting temperature is 83 C in 0.1 SSC (0.15 m NaCl plus 0.015 m sodium citrate) and 98 C in SSC. (iii) Buoyant density in cesium sulfate was 1.58 g/cm(3) compared to 1.64 g/cm(3) for single-stranded RNA. (iv) It gave rise to single-stranded RNA after denaturation. (v) The 12S RNA duplex contained both plus and minus strands of influenza virus. Labeled plus strands could be displaced by extraneous cold plus strands and extraneous (32)P-labeled plus strands could be incorporated into duplex after denaturation and reannealing.

Structure and function of bacteriophage R17 replicative intermediate ribonucleic acid. II. Properties of the parental labeled molecule

Replicative intermediate ribonucleic acid (RNA), designated RI, which contained parental RNA labeled with (32)P was separated by filtration through agarose from the nucleic acids prepared from (32)P-labeled RNA phage-infected Escherichia coli. A larger amount of ribonuclease-sensitive parental label was found in the rapidly sedimenting forms of RI than in the slower sedimenting forms, indicating that parental RNA is displaced to form a single-stranded tail. This result indicates that some phage RNA is generated by asymmetric semiconservative replication of RI, but it does not mean that a portion of the RI duplexes cannot be conserved during generation of phage RNA. Parental RNA was also found in double-stranded RNA with no apparent tails which sedimented with an S value of 13. This RNA was soluble in 2 m NaCl, and its sedimentation rate was unaffected by ribonuclease; nevertheless, single-strand scissions were produced by ribonuclease and were detected after the duplex was converted to its component single strands.

Ribonucleic acid synthesis by Escherichia coli C 3000/L after infection by the ribonucleic acid coliphage ZIK/1, and properties of the coliphage-induced double-stranged ribonucleic acid

1. The efficiency of extracting nucleic acids from Escherichia coli after five methods of obtaining cell lysis was determined. 2. The recovery of various nucleic acid species isolated after chromatography on methylated albumin-coated kieselguhr was also examined. 3. Double-stranded coliphage-induced RNA was isolated from infected bacteria and its resistance to ribonuclease digestion under various conditions determined. 4. The involvement of double-stranded RNA during the infection process was demonstrated. 5. The time-course of the syntheses in infected cells of double-stranded RNA, DNA, single-stranded coliphage and 16s ribosomal RNA, transfer RNA and ribosomal 23s RNA was examined. 6. It was demonstrated that the syntheses of DNA, transfer RNA and ribosomal RNA decreased 10-15min. after infection. 7. Synthesis of coliphage RNA commenced 10-15min. after infection and double-stranded RNA was also synthesized from about 10min. after coliphage adsorption.

Physical properties of single- and double-stranded coliphage ribonucleic acid

1. The physical characteristics of single- and double-stranded coliphage RNA with regard to their sedimentation behaviour in gradients of sucrose in high or low ionic conditions were examined. The effect of heat on their sedimentation characteristics was also determined. 2. Single-stranded coliphage RNA was found to exist in three different forms having sedimentation coefficients 28s, 20s and 12s. The latter two were interchangeable, depending on ionic strength. All three were almost equally infectious to spheroplasts. 3. Double-stranded coliphage RNA was found to be non-infectious to spheroplasts and had sedimentation coefficients 15s and 12s. Thermal denaturation gave rise to infectious single-stranded 12s RNA. 4. Four possible hypotheses on the mechanism of replication of coliphage RNA are discussed.