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R E Cannon

Publications and source records attributed to R E Cannon.

34 records · Page 2Linked to original sources
PubMed1986

Termination sequences in the control region of the Ad2-specific VARNA2 gene.

Both VARNA genes in the adenovirus genome are transcribed by host DNA-dependent RNA polymerase III. Nevertheless, late in infection the mass ratio of VARNA2 to VARNA1 in adenovirus-infected human KB or HeLa cells is about 1:40. This difference is most likely due to differences in promoter strength which may be attributed to sequence differences in the control regions of the two genes. To investigate this possibility, the two genes were cloned into separate plasmid molecules and their transcription efficiencies were compared in vitro. The VARNA2 gene was transcribed in vitro at least 50 times less efficiently than the VARNA1 gene. The competing strengths of the two genes were similar, which suggests that the B block sequence in the VARNA2 gene may be fully functional for sequestering factors. Therefore, the major difference must reside in the region upstream of the B block. By analyzing the hybrid RNAs transcribed from a hybrid gene and 27 fused genes in which only the control region of the VARNA1 gene was fused to various lengths of the 5'-flanking and the coding regions of the VARNA2 gene, one major and one minor termination site, which caused premature termination, were revealed downstream of the A block sequence and in the 5'-flanking region of the VARNA2 gene, respectively. The presence of termination sequences, a suboptimal interblock spacing, and an altered A block sequence in the control region may result in a weaker promoter in the VARNA2 gene.

Adenoviridae↗
PubMed1986

Functions of and interactions between the A and B blocks in adenovirus type 2-specific VARNA1 gene.

The internal transcriptional control region (ITCR) of VARNA1 gene consists of a 33-base-pair (bp) interblock sequence and two 12-bp sequence blocks that are highly conserved in most of the genes transcribed by RNA polymerase III. To define the functions of and study the interactions between the two blocks, we have constructed mutants with altered interblock sequence or spacing for transcription. The results of transcription efficiencies and competing strengths indicated that the interblock sequence was dispensable and the A and B blocks were essential for transcription control. One of the major functions of the interblock sequence was to maintain an optimal spacing for an intimate interaction between the two essential blocks. Shortening or elongating the interblock spacing in the mutants beyond this range drastically decreased the transcription efficiencies and competing strengths of these mutated genes. To further study how the interaction between the two blocks leads to initiation, the start sites and sizes of RNA products of the mutants were determined. When the interblock spacing was less than 105 bp, the wild-type start site was dictated by the A block after an interaction with the B block through proteins. However, when the interblock spacing was longer than 105 bp, several new start sites located closer to the B block were preferentially used. This suggests that new start sites may be dictated by the B block when its interaction with the A block is weakened by longer spacing. The mechanisms of interaction between the bipartite domain in this gene leading to initiation are different from those in tRNAs and Alu-family RNA genes.

Adenoviruses, Human↗
PubMed1985

An economical large scale procedure to purify E. coli amplifiable plasmids for DNA sequencing, in vitro transcription and in vitro mutagenesis.

A reproducible and economical procedure for obtaining a large and quantitative yield of highly purified covalently closed circular plasmid DNA is described. The procedure departs in several ways from more commonly used methods. These are a) avoidance of the use of CsCl, ethidium bromide and ultracentrifuge, b) enrichment of the plasmid DNA by selective denaturation of chromosomal DNA with an alkaline-SDS solution, c) enrichment of covalently closed circular plasmid DNA by extraction with acid-phenol, and d) removal of small degraded RNA fragments by molecular sieve chromatography after digestion with RNase A. The plasmid DNA prepared by this new procedure is free of contaminants and has been used for DNA sequencing, in vitro transcription, transformation and in vitro mutagenesis.

Base Sequence↗
PubMed1984

Effects of pesticides on cyanobacterium Plectonema boryanum and cyanophage LPP-1.

Cyanobacterium Plectonema boryanum IU 594 and cyanophage LPP-1 were used as indicator organisms in a bioassay of 16 pesticides. Experiments such as spot tests, disk assays, growth curves, and one-step growth experiments were used to examine the effects of pesticides on the host and virus. Also, experiments were done in which host or virus was incubated in pesticide solutions and then assayed for PFU. P. boryanum was inhibited by four herbicides: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 1,1-dimethyl-3-(alpha, alpha,alpha-trifluoro-m-tolyl)urea ( Fluometeron ), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (Atrazine), 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine ( Ametryn ). One insecticide, 2-methyl-2-(methylthio)-propionaldehyde O-( methylcarbamoyl )oxime (Aldicarb), also inhibited the cyanobacterium. Two insecticides inactivated LPP-1, O,O-dimethyl phosphorodithioate of diethyl mercaptosuccinate (malathion) and Isotox . Isotox is a mixture of three pesticides: S-[2-( ethylsulfinyl )ethyl]O,O-dimethyl phosphorothioate ( Metasystox -R), 1-naphthyl methylcarbamate ( Sevin ) and 4,4'-dichloro-alpha- (trichloromethyl) benzhydrom ( Kelthane ). Two pesticide-resistant strains of P. boryanum were isolated against DCMU and Atrazine. These mutants showed resistance to all four herbicides, which indicates a relationship between these phototoxic chemicals. The results indicate that P. boryanum may be a useful indicator species for phototoxic agents in bioassay procedures.

Bacteriophages↗
PubMed1976

The use of cellulose products to reduce agar concentration in microbiological media.

The use of agar in media for culturing microorganisms is fundamental to microbiological investigations. Shortages of agar have caused increased costs and difficulty in obtaining media. Evidence is presented for the use of carboxymethylcellulose (CMC), an inert compound, in conjunction with agar to reduce the concentration of agar necessary to achieve a solid plating surface. A variety of bacteria, blue-green bacteria, fungi, and a yeast were tested for growth on CMC agar media. T-2 bacteriophage and three cyanophages were tested for plaque-forming efficiency on CMC agar plates. Selective and differential media were also formulated with a CMC agar supplement. Growth of all microorganisms was comparable on CMC and agar control. Use of cellulose products provides a means of decreasing agar consumption without affecting successful cultivation of microorganisms.

Agar↗
PubMedDate not supplied

TGF alpha is dispensable for skin tumorigenesis in Tg.AC mice.

Alterations in growth factor signaling pathways frequently accompany the development and maintenance of epithelial neoplasia. Transforming growth factor alpha (TGF alpha) and its epidermal growth factor receptor have been thought to play an especially important role in epithelial neoplasia. In this study, mice were derived genetically deficient (null) in functional TGF alpha expression and carrying the Tg.AC/v-Ha-ras transgene. The goals were to determine if (a) papillomagenesis was dependent on TGF alpha and (b) progression to malignancy was dependent on TGF alpha expression. Groups of male and female mice heterozygous or homozygous for the TGF alpha null allele and hemizygous for the Tg.AC transgene were treated twice weekly for 10 or 15 wk with doses of 12-O-tetradecanoylphorbol-13-acetate (TPA) known to produce papillomas in Tg.AC mice. Papillomas were readily induced in both male and female TGF alpha null mice. Malignant progression of papillomas was observed in all TGF alpha null treatment groups. Additionally, we examined the response of TGF alpha null mice to full thickness dorsal wounds, a stimulus known to promote papillomagenesis in Tg.AC mice. As in the TPA study, papillomas were induced in both male and female TGF alpha null mice. These studies indicate that TGF alpha is not required for the induction and maintenance of papillomas nor is it essential for the malignant conversion of papillomas in Tg.AC mice.

Animals↗