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R F Weaver

Publications and source records attributed to R F Weaver.

15 recordsLinked to original sources
PubMed1991

Structural comparison of the Autographa californica nuclear polyhedrosis virus-induced RNA polymerase and the three nuclear RNA polymerases from the host, Spodoptera frugiperda.

A partial subunit structure has been determined for the novel RNA polymerase that is induced in fall armyworm (Spodoptera frugiperda) cells upon infection with the Autographa californica nuclear polyhedrosis virus (AcNPV). The putative structure includes nine polypeptides; the complexity of this structure is in accord with the high sedimentation coefficient (15S) estimated for this enzyme. A comparison of the putative structure of the virus-induced polymerase with those of the three host nuclear RNA polymerases shows that the structure of the viral polymerase is apparently unlike any of the host nuclear polymerases. This conclusion is reinforced by immunoblot experiments that show no cross-reactivity between the virus-induced polymerase and an antiserum directed against Drosophila RNA polymerase II. The virus-induced RNA polymerase appears at the onset of the late phase of infection and still appears when viral DNA synthesis is blocked by aphidicolin. Thus, the virus-induced polymerase seems to be composed of early viral products.

Animals↗
PubMed1991

Nucleotide sequence and transcript mapping of the HindIII F region of the Autographa californica nuclear polyhedrosis virus genome.

The organization of genes in the 2.95 kb EcoRI-SalI fragment (0.7 to 3.0 map units) located within the HindIII F region of the Autographa californica nuclear polyhedrosis virus genome was studied by a combination of DNA sequencing, Northern blot analysis, S1 mapping and primer extension analysis. In addition to the two divergent overlapping transcripts [leftward early (ES1) and rightward late (ES2)] previously reported, a third transcript which is present at 18 h p.i. and which also runs leftward, overlapping ES1 by 1600 nucleotides (nt) at the 3' end, was mapped to this region. The DNA sequence revealed the presence of three open reading frames (ORFs) of significant length. ORF-1 and ORF-2 correspond to the leftward transcripts, and code for potential polypeptides of 151 and 329 amino acids, respectively. ORF-3 which codes for a potential polypeptide of 167 amino acids is located on the opposite strand in a region for which no transcript mapping data are available. However, the conserved late gene promoter/cap site sequence (ATAAG) is present 23 nt upstream of the start of ORF-3.

Amino Acid Sequence↗
PubMed1990

Identifying the RNA polymerases that synthesize specific transcripts of the Autographa californica nuclear polyhedrosis virus.

Nuclear run-on assays carried out in the presence and absence of the RNA polymerase II inhibitor, alpha-amanitin, were used to determine the exact timing of the switch from inhibitor-sensitive transcription catalysed by host RNA polymerase II, to inhibitor-resistant transcription catalysed by the baculovirus-induced RNA polymerase. These studies revealed that the onset of alpha-amanitin-resistant transcription is just after 6 h post-infection, simultaneous with the beginning of the late phase of infection. They also showed that transcripts from the p26 gene in the HindIII Q/P region and the p35 gene in the HindIII K/Q region of the viral genome are synthesized by the host RNA polymerase II both early and late in infection. On the other hand, transcripts of the p10 gene in the HindIII Q/P region and the gamma transcripts in the HindIII K region are synthesized by the alpha-amanitin-resistant, virus-induced RNA polymerase late in infection.

Amanitins↗
PubMed1990

Overlapping divergent transcripts mapping to the HindIII F region of the Autographa californica nuclear polyhedrosis virus.

We have mapped a set of transcripts that cross the XhoI site in the HindIII F fragment of the genome of the Autographa californica nuclear polyhedrosis virus. These transcripts overlap at their 5' ends by about 550 bases and run in opposite directions. We have tentatively identified two open reading frames corresponding to the leftward transcript. The rightward transcript is present from 8 h post-infection (p.i.) to 24 h p.i.; the leftward transcripts are present from 2 h p.i. to 24 h p.i. The early (2 h) transcript is about 2.1 kb in size and its 5' end maps about 504 bp to the right of the XhoI site. Beginning at about 8 h p.i. a new transcription start site is used, about 80 bp downstream (to the left) of the first. The late (rightward) transcript is about 1.2 kb in size; its 5' end seems to be heterogeneous and maps about 44 to 60 bp to the left of the XhoI site. Late in infection transcription proceeds in both directions at the same time through the overlapping region of the DNA encoding these transcripts.

Animals↗
PubMed1990

Categorizing some early and late transcripts directed by the Autographa californica nuclear polyhedrosis virus.

Using an S1 mapping assay on RNA from Spodoptera frugiperda cells infected by the Autographa californica nuclear polyhedrosis virus in the presence and absence of cycloheximide and aphidicolin, we can distinguish three classes of transcripts. First, there are those whose synthesis is blocked by the DNA synthesis inhibitor aphidicolin and which are therefore late transcripts. These include the late transcript of the 39K gene and a late leftward transcript across the XhoI site in the HindIII-F region. Second, there are those whose synthesis is not blocked by aphidicolin, but whose accumulation is inhibited by the protein synthesis inhibitor cycloheximide and which are therefore presumably delayed early genes. These include the p26 transcript(s), the early 39K transcript and the alpha 2 transcript in the HindIII-K/Q region. Third, there are those whose accumulation is not affected or is enhanced by cycloheximide. These are not necessarily immediate early transcripts, but their response to cycloheximide is clearly different from that of those in the second class. They include the alpha 1 and alpha 3 transcripts in the HindIII-K/Q region and the early leftward transcript across the XhoI site in the HindIII-F region.

Animals↗
PubMed1989

Studies on the control region of the p10 gene of the Autographa californica nuclear polyhedrosis virus.

5' deletion mutants of the Autographa californica nuclear polyhedrosis virus very late p10 gene promoter have been prepared and subjected to a transient expression assay in infected Spodoptera frugiperda cells. The control plasmid contained the chloramphenicol acetyltransferase (CAT) reporter gene under the control of the p10 promoter, which was included in a 230 bp sequence upstream from the p10 translation initiation codon. The control plasmid also contained a segment of the hr5 enhancer downstream from the CAT gene. Promoter activity was unaffected by 5' deletion to position -77, which lies about 11 bp upstream from the p10 cap site. However, deletion of 12 more bp completely eliminated p10 promoter activity. Thus, the 5' border of the p10 promoter lies downstream from position -77, and the region between positions -77 and -65 contains an element that is important to promoter activity. This is the region that is conserved near the cap sites of late baculovirus genes. Our studies also show that transient expression of CAT under the control of the p10 promoter and hr5 enhancer is higher when transfection occurs prior to infection by virus.

Animals↗
PubMed1986

Physical mapping of temporally regulated, overlapping transcripts in the region of the 10K protein gene in Autographa californica nuclear polyhedrosis virus.

We investigated transcriptional activity in the region of a gene for a major late protein (10 kilodaltons) of Autographa californica nuclear polyhedrosis virus. This 10K protein gene spans an HindIII cleavage site, with the 5' end of the gene located in the HindIII-Q fragment and the 3' end in the HindIII-P fragment. Northern blot analysis showed that there were at least four transcripts mapping in this region, two that are present maximally at 12 h (1,500 and 1,100 bases in length) and two that are present at 24 h (750 and 2,500 bases in length). Northern blot analysis also suggested that these transcripts overlap. S1 mapping identified the precise positions of the transcripts and confirmed the overlap. The 1,500- and 1,100-base transcripts share a common 5' end, about 1,056 bases upstream from the HindIII-P-Q boundary; the 750- and 2,500-base transcripts share a common 5' end, about 303 bases upstream from the HindIII-P-Q boundary. The 1,100-base transcript terminates in the Q fragment, about 234 bases from the HindIII-P-Q boundary. The other three transcripts all end in the P fragment. Both the 1,500- and the 750-base transcripts terminate approximately 240 bases from the HindIII-P-Q boundary. The 2,500-base transcript exhibits 3'-end heterogeneity, ending around 2,046 bases from the HindIII-P-Q boundary. Therefore, three different transcripts (1,500, 750, and 2,500 bases in length) contain the complete 10K protein coding region. A fourth transcript (1,100 bases in length) overlaps the 750-base 10K protein gene transcript by 70 bases.

DNA Restriction Enzymes↗
PubMed1979

Mapping of RNA by a modification of the Berk-Sharp procedure: the 5' termini of 15 S beta-globin mRNA precursor and mature 10 s beta-globin mRNA have identical map coordinates.

We have used a modification of the Berk-Sharp technique to determine that the 5' termini of the mouse 15 S beta-globin precursor and the mature mRNA have identical map coordinates. The modification involves the use of 5' (or 3') terminally labeled probes; it allows the detection of the precursor in the presence of excess mature mRNA.

Animals↗
PubMed1977

CNDO molecular orbital calculations on porphyrins--I. Ground and excited states of porphyrin, divinylporphyrin and tetraphenylporphyrin.

Semi-empirical CNDO/2 MO calculations are reported for the ground states of porphyrin, 2,4-divinylporphyrin (DVP), and alpha, beta, gamma, delta-tetraphenylporphyrin (TPP). Results for TPP refer to the conformation with all phenyl groups perpendicular to the porphyrin ring, calculated to be 108 kJ mol-1 more stable than the coplanar conformation. The substituents withdraw electron density where they are attached to the porphyrin ring, increasing selected orbital energies. The vinyl groups also modify the electron population at nitrogen. CNDO/S calculations with extensive configuration interaction are reported for excited states. The lowest singlet states are closely similar in energy and composition for all three molecules, except for an extra state and more complex compositions in DVP above 3 eV. The lowest triplet states of porphyrin and DVP are very similar, while those of TPP are comparable in energy or composition but not both. Experimental data on the excited states are broadly consistent with the calculations, although comparisons for the excited triplets are tentative.

Molecular Conformation↗
PubMed1977

CNDO molecular orbital calculations on porphyrins--II. Ground states of dilithium and disodium porphyrin.

CNDO/2 calculations are reported for dilithium and disodium porphyrin. The total energy is calculated as a function of the metal-ring distance for symmetrical (D4h) structures. For dilithium porphyrin, the equilibrium metal-ring distance is 0.87 A and the metal-metal vibrational frequency is 123 cm-1. For disodium porphyrin, the distance is 1.64 A and the frequency is 77 cm -1. Little mixing of metal and porphyrin orbitals takes place; the two lowest unoccupied and the two highest occupied MOs hardly differ from those in porphyrin, but lower MOs are considerably rearranged.

Lithium↗
PubMed1977

Structural studies on the polyhedral inclusion bodies, virions, and DNA of the nuclear polyhedrosis virus of the cotton bollworm Heliothis zea.

The polyhedral inclusion body of the cotton bollworm nuclear polyhedrosis virus contains virions occluded in an orthogonal crystalline matrix. The virions appear as rods or, more frequently, as oval structures that form upon bending of the nucleocapsid within the viral membrane. The nucleocapsid consists at least of DNA surrounded by a capsid composed of subunits, possibly helically arranged. The viral DNA is circular and supercoiled. It is heterogenous in size with contour lengths ranging from 15 to 45 mum.

Animals↗
PubMed1976

Photoreceptor pigment that induces differentiation in the slime mold Physarum polycephalum.

An extract of small molecules (molecular weight less than 500) of the slime mold Physarum polycephalum undergoes a shift in ultraviolet-visible absorption spectrum upon illumination. This illumination also confers on the extract the ability to induce sporulation when injected into a starved, unilluminated slime mold. The spectral shift and appearance of the sporulation-inducing activity both occur regardless of whether the illumination is carried out on an intact slime mold or on the plasmodium-free extract itself. Thin-layer chromatography resolves the slime mold extract into four major visible fractions. One of these has high sporulation-inducing activity after illumination in vitro.

Cell Differentiation↗