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D Dressler

Publications and source records attributed to D Dressler.

At least 127 records · Page 7Linked to original sources
PubMed1974

On the chemical nature of transfer factor.

Two transfer factors prepared in an experimental animal model, the guinea pig, have been tested for their susceptibility to various enzymes of known specificity. The biological activity of these immune response mediators can be destroyed by RNase III, an enzyme that degrades duplex RNA. It, therefore, appears that these transfer factors consist entirely or partly of double-stranded RNA.

Animals↗
PubMed1974

Transfer factor.

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Animals↗
PubMed1973

The amplification of ribosomal RNA genes involves a rolling circle intermediate.

During the development of Xenopus oocytes there is a special DNA synthesis that leads to a thousandfold amplification of the genes that code for ribosomal RNA. We have used the electron microscope to study this process. Our primary observation is the presence of ribosomal DNA in rolling-circle intermediates at the time of amplification. We believe that these intermediates are involved in the amplification process, and as such offer the first example of the involvement of a rolling circle in the replication of eukaryotic DNA.

Animals↗
PubMed1972

Adenovirus-2 DNA contains an inverted terminal repetition.

Denaturation and renaturation of the adenovirus-2 chromosome (a duplex rod) generates single-stranded circles of unit length. These circles can be opened into linear DNA molecules by digestion with exonuclease III, indicating that hydrogen bonding between the two ends of an adenovirus strand is responsible for maintaining the rod in a circular state.The formation of adenovirus single-stranded circles, and their sensitivity to exonuclease III, indicate that the mature adenovirus-2 DNA molecule contains an inverted terminal repetition. That is, the base sequence at one end of the molecule is inverted and appears again at the other end of the molecule. This is the first example of such a structure, and its function is unknown.

Adenoviridae↗
PubMed1972

Initiation and reinitiation of DNA synthesis during replication of bacteriophage T7.

In its first round of replication, the T7 chromosome follows a simple pattern, as viewed in the electron microscope. The iniation of DNA synthesis occurs about 17% from the genetic left end of the viral DNA rod. Bidirectional DNA synthesis from this origin then generates a replicating intermediate that we call an "eye form." In the eye form, when synthesis in the leftward direction reaches the left end of the viral chromosome, the molecule is converted into a Y-shaped replicating rod. The remaining growing point continues synthesis rightward, until presumably it runs off the right end of the DNA rod, thus terminating replication. Numerous T7 chromosomes were found in which a second round of replication had begun before the first round had finished. Analysis of these reinitiated DNA molecules showed that the second round of replication, like the first, began 17% from the end of the chromosome and involved bidirectional DNA synthesis.

Centrifugation, Density Gradient↗
PubMed1972

Regions of single-stranded DNA in the growing points of replicating bacteriophage T7 chromosomes.

In partially replicated T7 chromosomes, the points where parental strands are separating and new DNA is being synthesized can be seen in the electron microscope to contain regions of single-stranded template DNA. The single-stranded regions are located on only one of the two daughter arms of the replicating chromosome. Inman and Schnös observed such single-stranded regions in 50% of the growing points of replicating lambda DNA, and, as reported in this paper, we find them in about 85% of the growing points of T7 DNA. Both studies support the conclusion that DNA synthesis involves the direct elongation of one daughter strand in the growing point. Evidently, this elongation is accompanied by the unwinding of the parental double helix to expose a region of single-stranded DNA which is then converted to the duplex state by a discontinuous mechanism involving the synthesis of DNA fragments.

Centrifugation, Density Gradient↗
PubMed1970

The rolling circle for phi X DNA replication. 3. Synthesis of supercoiled duplex rings.

During varphiX duplex ring synthesis, the first supercoils to acquire radioactivity after the addition of tritiated thymidine are labeled only in their negative strands. In longer pulses, this asymmetry of labeling progressively disappears. This finding supports the rolling circle model for DNA replication due to the structural asymmetry of its replicating intermediate, but is not predicted by the Cairns or Yoshikawa models.

Carbon Isotopes↗
PubMed1970

The rolling circle for phiX DNA replication. II. Synthesis of single-stranded circles.

varphiX-infected cells have been allowed to incorporate tritiated thymidine late in the phage life cycle when single-stranded circles are the product of DNA synthesis. Virtually all of the radioactivity is recovered in a continuum of actively replicating viral DNA molecules. These molecules are termed rolling circle intermediates because they are characterized by three structural properties. They possess positive strands that are longer than the length of a mature viral genome, and negative strands that are covalently closed single-stranded circles. The 3' termini of the long positive strands lie upon the template rings, while the 5' ends are free in solution. From these experimental data, the basic mode of synthesis is deduced to involve the continuous elongation of the open positive strand by endless copying around the circular negative strand template. As new bases are added to the template-bound (3') end of the positive strand, the distal (5') end is displaced from the template ring as a single-stranded tail of increasing length. It is the tail which serves as the source of material for progeny chromosomes. These data confirm our characterization of this varphiX intermediate, which initially was based only on the possession of long positive strands, and extend this characterization to include experimental statements about the circular nature of the template DNA strand, and the 5' to 3' direction of polynucleotide chain growth within the intermediate. Moreover, the description can now be applied to all of the molecules which acquire label during a pulse.

Coliphages↗