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D E Burbank

Publications and source records attributed to D E Burbank.

32 records · Page 2Linked to original sources
PubMed1986

Restriction endonuclease activity induced by NC-1A virus infection of a Chlorella-like green alga.

A type II restriction endonuclease, CviBI, was isolated from a eukaryotic, Chlorella-like green alga infected with the dsDNA containing virus NC-1A. The enzyme recognizes the sequence GANTC and cleaves DNA between the G and A. Methylation of deoxyadenosine in the GANTC sequence probably inhibits enzyme activity. In vitro CviBI cleaves host nuclear DNA but not viral DNA. A survey of 18 other viruses which infect the same Chlorella sp. revealed that infection with 5 of these viruses also induced a restriction endonuclease which cleaves DNA into the same size fragments as CviBI.

Base Sequence↗
PubMed1986

Characterization of viruses infecting a eukaryotic Chlorella-like green alga.

Nineteen plaque-forming viruses of the unicellular, eukaryotic Chlorella-like green alga, strain NC64A, were isolated from various geographic regions in the United States and characterized. Like the previously described virus, PBCV-1, all of the new viruses were large polyhedrons, sensitive to chloroform, and contained large dsDNA genomes of ca. 300 kbp. All of the viral DNAs contained 5-methyldeoxycytidine which varied from 0.1 to 47% of the deoxycytidine. In addition, 10 of the viral DNAs contained N6-methyldeoxyadenosine which varied from 8.1 to 37% of the deoxyadenosine. These viruses, along with 11 previously described viruses which replicate in the same Chlorella host, were grouped into 11 classes based on at least one of the following properties: plaque size, reaction with PBCV-1 antiserum, or the nature and abundance of methylated bases in their genomic DNA.

Base Composition↗
PubMed1986

Infection of a Chlorella-like alga with the virus PBCV-1: transcriptional studies.

Infection of the unicellular, eukaryotic Chlorella-like green alga NC64A by the large dsDNA containing virus PBCV-1 immediately reduced host RNA synthesis. Chloroplast rRNAs, but not cytosolic rRNAs, were degraded following viral infection. Northern blot analysis utilizing four cloned fragments of PBCV-1 DNA as probes, which represent about 12% of the viral genome, revealed several properties of PBCV-1 transcription: A few viral transcripts were detected within 5 min after infection. Each PBCV-1 DNA clone hybridized to both early and late transcripts which implies that early and late genes are dispersed throughout the viral genome. The transition from early to late transcription occurred between 40 and 60 min after infection coincident with the onset of viral DNA synthesis. Three of the four DNA clones hybridized to transcripts which additively were larger than the corresponding DNA probe. This could reflect RNA processing, presence of overlapping genes, or transcription from both DNA strands. A few, but not all, early transcripts were synthesized in the presence of cycloheximide. This suggests that the virus either carries in its own RNA polymerase or uses a host RNA polymerase for very early viral transcription and that synthesis of additional, later transcripts depends on translation of an early gene product(s).

Chlorella↗
PubMed1986

Restriction endonuclease activity induced by PBCV-1 virus infection of a Chlorella-like green alga.

An enzyme was isolated from a eucaryotic, Chlorella-like green alga infected with the virus PBCV-1 which exhibits type II restriction endonuclease activity. The enzyme recognized the sequence GATC and cleaved DNA 5' to the G. Methylation of deoxyadenosine in the GATC sequence inhibited enzyme activity. In vitro the enzyme cleaved host Chlorella nuclear DNA but not viral DNA because host DNA contains GATC and PBCV-1 DNA contains GmATC sequences. PBCV-1 DNA is probably methylated in vivo by the PBCV-1-induced methyltransferase described elsewhere (Y. Xia and J. L. Van Etten, Mol. Cell. Biol. 6:1440-1445). Restriction endonuclease activity was first detected 30 to 60 min after viral infection; the appearance of enzyme activity required de novo protein synthesis, and the enzyme is probably virus encoded. Appearance of enzyme activity coincided with the onset of host DNA degradation after PBCV-1 infection. We propose that the PBCV-1-induced restriction endonuclease participates in host DNA degradation and is part of a virus-induced restriction and modification system in PBCV-1-infected Chlorella cells.

Base Sequence↗
PubMed1986

Replication of the algal virus PBCV-1 in UV-irradiated Chlorella.

The large dsDNA algal virus, PBCV-1, replicates in UV-irradiated Chlorella, albeit more slowly and with a smaller burst size than in untreated Chlorella. Irradiated cells are unable to form colonies, and endogenous RNA and DNA synthesis are reduced to background levels. Thus a fully function host nucleus is not required for PBCV-1 replication.

Chlorella↗
PubMed1985

DNA methylation of viruses infecting a eukaryotic Chlorella-like green alga.

The genomic DNAs of the eukaryotic Chlorella-like green alga, strain NC64A, and eleven of its viruses all contain significant levels of 5-methyldeoxycytidine. In addition, the host DNA as well as six of the viral DNAs also contain N6-methyldeoxyadenosine. At least some of the methylated bases in the host reside in different base sequences than the methylated bases in the viruses as shown by differential susceptibility to restriction endonuclease enzymes. This suggests that the viruses encode for DNA methyltransferases with sequence specificities different from that of the host enzyme.

Base Composition↗
PubMed1985

Lytic viruses infecting a Chlorella-like alga.

A number of viruses which form plaques on the unicellular, eukaryotic, Chlorella-like green alga, strain NC64A, were isolated from fresh water ponds and rivers in Illinois, North Carolina, and South Carolina. The viruses were large polyhedrons (160 to 190 nm in diameter) and contained dsDNA genomes of ca. 300 kbp. All of the viral DNAs hybridized with DNA from the previously described PBCV-1 virus. However, the viruses, even many of those isolated from the same water sample, could be distinguished from one another by DNA restriction endonuclease digestion. The viruses, including PBCV-1, were grouped into five classes by their resistance to certain DNA restriction endonucleases. Presumably the DNAs in the five classes contain different types or amounts of modified bases.

Chlorella↗
PubMed1984

Infection of a Chlorella-like alga with the virus, PBCV-1: ultrastructural studies.

Ultrastructural studies revealed that the virus, PBCV-1, adsorbs to the surface of the Chlorella-like green alga NC64A and enzymatically digests a portion of the host cell wall. The viral DNA is then released into the interior of the cell leaving an empty capsid on the surface. Thus uncoating of the viral genome occurs at the surface of its host. PBCV-1 also adsorbs to and digests the host wall of either heat-killed, methanol-extracted, or purified cell wall fragments.

Chlorella↗
PubMed1984

Structural proteins and lipids in a virus, PBCV-1, which replicates in a Chlorella-like alga.

PBCV-1, a large dsDNA-containing virus which replicates in a Chlorella-like green alga, is composed of approximately 64% protein, 25% DNA, and 5-10% lipid on a weight basis. Polyacrylamide gel electrophoresis of the dissociated virus particle resolves 50 to 60 proteins which range in apparent molecular weight from 10,000 to 135,000. Two of these proteins are glycoproteins and at least four are located on the viral surface. The major lipids are phosphatidyl choline, phosphatidyl ethanolamine, and an unidentified component. The effect of organic solvents, surfactants, and chelating and reducing agents on viral infectivity and ultrastructure are reported. Inhibitor studies established that PBCV-1 protein synthesis occurs on cytoplasmic ribosomes.

Chlorella↗
PubMed1982

Viruses of symbiotic Chlorella-like algae isolated from Paramecium bursaria and Hydra viridis.

We previously reported that isolation of symbiotic Chlorella-like algae from the Florida strain of Hydra viridis induced replication of a virus (designated HVCV-1) in the algae. We now report that isolation of symbiotic Chlorella-like algae from four other sources of green hydra and one source of the protozoan Paramecium bursaria also induced virus synthesis. Algae from one of these hydra contained a virus identical to HVCV-1 (based on its rate of sedimentation, buoyant density, reaction to HVCV-1 antiserum, and DNA restriction fragments) whereas algae from the other three hydra contained another similar, but distinct, virus (designated HVCV-2). The virus from the paramecium algae (designated PBCV-1) was distinct from both HVCV-1 and HVCV-2. The symbiotic algae in the hydra could also be distinguished ultrastructurally. Chloroplasts of both algae that produced HVCV-1 lacked a pyrenoid whereas chloroplasts of the other three symbiotic algae contained pyrenoids. Since all symbiotic eukaryotic algae we have examined have had virus, a potential viral role in symbiosis is suggested.

Journal Article↗
PubMed1980

Semiconservative synthesis of single-stranded RNA by bacteriophage phi 6 RNA polymerase.

The RNA polymerase in the nucleocapsid of Pseudomonas phaseolicola bacteriophage phi 6 transcribed large, medium, and small single-stranded RNA from the viral double-stranded RNA genome by a semiconservative (displacement) mechanism. Approximately 23%, 63%, and 65% of the nucleocapsid particles in the assay mixture synthesized at least one round of large, medium, and small single-stranded RNA molecules, respectively. Some of these particles reinitiated synthesis such that an average of 1.5 large, 33 medium, and 24 small single-stranded RNAs were synthesized from each double-stranded RNA.

Bacteriophages↗
PubMed1980

In vitro translation of the three bacteriophage phi 6 RNAs.

In vitro translation of the three single-stranded RNAs transcribed in vitro by bacteriophage phi 6 RNA polymerase revealed that the large RNA codes for phage proteins P1, P2, P4, and P7, the medium RNA codes for P3, P6, and P10, and the smaller RNA for P5, P8, and P9.

Chromosome Mapping↗
PubMedDate not supplied

Chlorella viruses encode multiple DNA methyltransferases.

The >320 kb dsDNA genomes of 16 viruses which infect Chlorella strain NC64A and 5 viruses infecting Chlorella strain Pbi were tested for their sensitivity/resistance to more than 80 DNA restriction endonucleases. From the known methylation sensitivities of these enzymes to site-specific 5-methylcytosine and N6-methyladenine DNA modifications, we deduce that the 16 NC64A viruses encode at least 13 different sequence-specific DNA methyltransferases and the 5 Pbi viruses encode at least 7 sequence-specific DNA methyltransferases. Each DNA methyltransferase has a 2 to 4 base pair DNA recognition sequence. Some individual viruses encode as many as ten different DNA methyltransferases, making these chlorella virus genomes among the most concentrated sources of DNA methyltransferase genes known.

Chlorella↗