All intact subunit RNAs from Rous sarcoma virus contain poly (A)

Evidence that the genome of hepatitis A virus consists of single-stranded RNA

Nucleic acid was extracted from purified hepatitis A virus, radiolabeled with 125I, and shown to consist of single-stranded RNA which sediments at 35S and contains sequences of polyadenylic acid. These findings are consistent with hepatitis A virus being a member of the genus Enterovirus within the family Picornaviridae.

Characterization of intracellular viral RNA in interferon-treated cells chronically infected with murine leukemia virus

We have recently found that Moloney murine leukemia virus assembles within cytoplasmic vacuoles of chronically infected NIH/3T3 cells rather than at their surface (submitted for publication). In the present study we found that if these cells were treated with interferon (IF) for 24 to 48 h the intracellular virus particles accumulated at a two- to threefold-higher level than that observed in untreated cells. Nevertheless, despite this accumulation, no difference between IF-treated and untreated cells was observed in the amount of the total cytoplasmic viral RNA or in its 35S or 21S species. When cellular virions were sedimented from the cytoplasmic fraction, a markedly higher amount of viral RNA was detected in the viral pellet of IF-treated cells than was detected in untreated cells, whereas the amount of viral RNA left in the virus-free cytoplasm of IF-treated cells was much lower than that in the untreated cells. Furthermore, the amount of the cytoplasmic polyriboadenylic acid-containing viral RNA was also remarkably higher in the IF-treated cells. Viral polyribosomes appeared to be fully functional in IF-treated cells, since no effect of IF on viral protein synthesis could be detected. Analysis of the nuclear viral RNA showed no difference between IF-treated and untreated cells after 24 h of IF treatment. Both contained a comparable amount of 35S viral RNA. However, at 48 h a significant accumulation of viral RNA was observed in the nucleus of the IF-treated cells as compared with the untreated cells, although in both cases only 35S species were evident. This accumulation appeared to activate a degradation process which destroyed nuclear viral RNA, since a dramatic shift toward smaller-sized molecules of viral RNA and a remarkable reduction in its amount were observed after 72 h of IF treatment.

The RNA of human coronavirus OC-43

A homogeneous RNA complex with a sedimentation coefficient of 70 S and an apparent molecular weight of approximately 6.1 × 10⁶ was released from purified ³²P-labeled, mouse-brain-derived OC-43 virus after treatment with 1% sodium dodecyl sulfate (SDS) for 15 min at 23°. The complex was highly susceptible to heat, releasing 4 S RNA fragments at 37° and breaking down to fragments of 4–70 S at 60°; it was also degraded by centrifugation through dimethyl sulfoxide gradients. Unlike tobacco mosaic virus or Rous sarcoma virus RNA, OC-43 RNA prepared by extraction with phenol-SDS or phenol-chloroform degraded into a range of fragments with coefficients of 15–55 S; 4 S RNA was also present as a minor component. This suggests that (a) extensive nicking of a large RNA molecule has occurred during viral growth, due to ribonucleases which are inactivated during phenol extractions; (b) heterogeneity for OC-43 RNA is not due to internal ribonuclease activity and fragments are held together by noncovalent linkages much weaker than those present in the 70 S retroviral RNA complex, or by small proteins; or, most probably, (c) a combination of extensive nicking and weak noncovalent linkages results in the heterogeneous denaturation products.

Mapping of poly(A) sequences in the electron microscope reveals unusual structure of type C oncornavirus RNA molecules

We have synthesized a convenient electron microscope label for mapping poly(A) sequences. Short lengths of poly(dT) are polymerized onto nicked circular SV40 DNA with the enzyme terminal deoxynucleotidyl transferase. An RNA or DNA molecule of interest is treated with glyoxal, hybridized briefly with the poly(dT) circles, and spread for microscopy; poly(A) stretches are clearly marked because they are attached to the poly(dT) on the easily recognized SV40 duplex circles. The RNAs of several type C oncornaviruses were examined by this method. The endogenous feline virus(RD-114), the endogenous baboon virus (BKD), and the woolly monkey sarcoma virus (WoMV) all contain a dimer of RNA subunits held together in a central secondary structure feature we call the dimer linkage structure. Both ends distal to the dimer linkage structure hybridize to the SV40-poly(dT). Assuming both poly(A)s are on the 3' ends of the subunits and that both subunits are identical, the two identical subunits are held together by interactions between sequences close to the 5' ends.