Comparison of the 3' termini of discrete segments of the double-stranded ribonucleic acid genomes of cytoplasmic polyhedrosis virus, wound tumor virus, and reovirus

Homologous Terminal Sequences in the Double-Stranded RNA Genome Segments of Cytoplasmic Polyhedrosis Virus of the Silkworm Bombyx mori

The 3'-terminal regions (20 to 32 residues) of the genome double-stranded RNA (dsRNA) segments of cytoplasmic polyhedrosis virus were sequenced. The dsRNAs, which were labeled at their 3' termini by incubation with [5'-(32)P]pCp and T4 RNA ligase, were denatured and resolved into the plus and minus strands by agarose-urea gel electrophoresis. Ten single-stranded RNAs thus obtained from the five dsRNA segments IV, V, VIII, IX, and X were sequenced by postlabeling methods. Common 3'-terminal sequences, -GUUAGCC and -UUACU, were found in the plus and minus strands, respectively, of all five dsRNA segments. However, adjacent sequences diverged and were considerably variable. The homologous sequences found in the 3' end may be important recognition signals for viral RNA polymerases and for assembly of the genome segments.

Variant dsRNAs associated with transmission-defective isolates of wound tumor virus represent terminally conserved remnants of genome segments

Variant double-stranded RNAs are often associated with the genome of transmission-defective isolates of wound tumor virus. These RNAs are replicated and packaged into virus particles in systemically infected plants and are transcribed in vitro by the virion-associated transcriptase. Direct physical evidence that the variant RNAs are remnants of particular WTV genome segments was provided by molecular hybridization studies. Subsequently, ribonuclease T1 digestion products of 3'-end-labeled genome and remnant RNAs were analyzed by one- and two-dimensional electrophoretic techniques. One-dimensional partial and complete digestion patterns were indistinguishable, indicating that the guanosine positions relative to the 3' terminus of the corresponding strands of a particular genome segment and its remnant RNA are the same for at least 40 nucleotides from each end. Fingerprints of the 3' terminal ribonuclease T1-resistant fragments were identical, showing that the nucleotide composition of the 3' terminal ends of the corresponding strands of a particular genome segment and its remnant RNA are also identical. These results indicate that variant RNAs associated with transmission-defective WTV isolates are formed by deletion of an internal portion (as much as 85%) of genomic RNA segments yielding terminally conserved genomic remnants that are functional with respect to transcription, replication, and packaging.

Properties and location of poly(A) in Rous sarcoma virus RNA

The poly(A) sequence of 30 to 40S Rous sarcoma virus RNA, prepared by digestion of the RNA with RNase T(1), showed a rather homogenous electrophoretic distribution in formamide-polyacrylamide gels. Its size was estimated to be about 200 AMP residues. The poly(A) appears to be located at or near the 3' end of the 30 to 40S RNA because: (i) it contained one adenosine per 180 AMP residues, and because (ii) incubation of 30 to 40S RNA with bacterial RNase H in the presence of poly(dT) removed its poly(A) without significantly affecting its hydrodynamic or electrophoretic properties in denaturing solvents. The viral 60 to 70S RNA complex was found to consist of 30 to 40S subunits both with (65%) and without (approximately 30%) poly(A). The heteropolymeric sequences of these two species of 30 to 40S subunits have the same RNase T(1)-resistant oligonucleotide composition. Some, perhaps all, RNase T(1)-resistant oligonucleotides of 30 to 40S Rous sarcoma virus RNA appear to have a unique location relative to the poly(A) sequence, because the complexity of poly(A)-tagged fragments of 30 to 40S RNA decreased with decreasing size of the fragment. Two RNase T(1)-resistant oligonucleotides which distinguish sarcoma virus Prague B RNA from that of a transformation-defective deletion mutant of the same virus appear to be associated with an 11S poly(A)-tagged fragment of Prague B RNA. Thus RNA sequences concerned with cell transformation seem to be located within 5 to 10% of the 3' terminus of Prague B RNA.

Comparison of the structure and polypeptide composition of three double-stranded ribonucleic acid-containing viruses (diplornaviruses): cytoplasmic polyhedrosis virus, wound tumor virus, and reovirus

Iodination of reovirus, cytoplasmic polyhedrosis virus (CPV), and wound tumor virus (WTV), and their respective subviral forms, followed by analysis of the labeled polypeptides by using polyacrylamide gel electrophoresis, has been used to compare the protein contents of these three diplornaviruses. This approach, when combined with electron microscopy and buoyant density determinations, appears capable of localizing individual polypeptides in some of the viral and subviral forms. CPV (p = 1.435 g/cm(3)) seems to resemble reovirus cores (p = 1.440 g/cm(3)) in both ultrastructure and polypeptide composition. CPV is composed of five polypeptides with molecular weights of about 151,000, 142,000, 130,000, 67,000, and 33,000. The polyhedral matrix, which in nature encapsulates the virions, is, in turn, composed mainly of two polypeptide species with molecular weights of about 30,000 and 20,000, and several minor proteins. The proteins of WTV consist mainly of four species of polypeptide with molecular weights of about 156,000, 122,000, 63,000, and 44,000, and several minor components. These molecular weight determinations are consistent with the hypothesis that, as has been suggested for reovirus, the viral proteins of CPV and WTV seem to be coded for by monocistronic mes senger RNA molecules transcribed from distinct segments of the double-stranded RNA viral genomes.