Related DNA Sequences Research Articles

In vitro‐labeled DNA for detecting viral genomes in multiple sclerosis

Papovaviruses appear to be neurotropic and one, JC virus, is implicated as the cause of one type of demyelinating disease, progressive multifocal leukoencephalopathy. To investigate whether human papovaviruses play a role in multiple sclerosis, radioactively labeled DNA from BK virus, human papilloma virus, and simian virus 40 was used as a probe in order to detect related unlabeled DNA sequences in DNA isolated from multiple sclerosis brain and/or spinal cord. Labeled viral probes were denatured and DNA allowed to reassociate in the presence of excess unlabeled DNA from multiple sclerosis tissue or from controls. The reassociation rate of the probe is proportional to the concentration of viral DNA present, and an increase in the reassociation rate of the probe over that of control reactions would indicate the presence of unlabeled viral DNA in multiple sclerosis cellular DNA. However, addition of DNA derived from multiple sclerosis patients did not increase rates of reassociation of viral probes. Known human papovaviruses probably have no role in the pathogenesis of multiple sclerosis.

Lack of infectivity of the endogenous avian leukosis virus-related genes in the DNA of uninfected chicken cells

The infectivity of the avian leukosis virus-related genes in the DNA of four genetically distinct types of chicken cells was determined. Infectious DNA of Rous-associated virus-O(RAV-O) was obtained from V- chicken cells which were experimentally infected with RAV-O and from V+tvbs chicken cells, which spontaneously produced RAV-O and were sensitive to exogenous RAV-O infection. However, infectious DNA of RAV-O was not obtained from uninfected V- chicken cells or from V+tvbr chicken cells, which spontaneously produced a low titer of RAV-O but were resistant to exogenous RAV-O infection. No detectable amplification of the RAV-O related DNA sequences in the V+tvbs cells was found by hybridization of RAV-O 125I-labeled RNA to the DNAs of V+tvbs and uninfected V- cells. These results indicate that the endogenous avian leukosis virus-related genes in uninfected V- and V+tvbr cells differ from the RAV-O proviruses in RAV-O-infected V- and V+tvbs cells. The lack of infectivity of the DNA of V+tvbr cells is consistent with the hypothesis that the endogenous RAV-O genome in V+tvbr cells is linked to a cis-acting control element, which results in its inefficient expression.

Related base sequences in the DNA of simple and complex organisms. V. The specificity of interactions between oligonucleotides and denatured DNA

A mixture of differentially labeled mouse and Bacillus subtilis DNA was used as a source of oligodeoxynucleotides of chain lengths from 15 to 40 nucleotides. The extent of interaction of these oligonucleotides with homologous or heterologous DNA bound to membrane filters was measured. The specificity of such interactions increases with chain length and with the incubation temperature. The thermal stability of the complexes is a function of chain length. Homologous oligonucleotide/DNA duplexes of B. subtilis are more stable than those of mouse of corresponding size, consistent with the incidence of partially related base sequences in mouse DNA. Oligonucleotides in this size range are also able to recognize partially complementary base sequences in the DNA of closely related organisms. This approach shows promise as a means of obtaining quantitative estimates of base sequence divergence between the DNAs of related organisms.

Related base sequences in the DNA of simple and complex organisms. I. DNA-DNA duplex formation and the incidence of partially related base sequences in DNA.

A comparative study has been made of the reactions of bacteriophage T4, B. subtilis,and mouse DNA with homologous DNA trapped on a membrane filter. The variation of reaction rate with temperature provides information as to the number of unique and partially related base sequences. The thermal stability of the duplexes formed at various temperatures has been used as a criterion of the extent of base pairing. These studies suggest that no closely related base sequences exist within the T4 genome. Similar results were obtained with Bacillus subtilisDNA although the data suggest the possibility of some very distant intragenome homologies. In contrast, mouse DNA contains so many related base sequences that the predominant reaction product is always one containing partially complementary strands. These results suggest that gene duplication has been a major mechanism operative in the increase of DNA content of metazoans through evolution. The relationship between the existence of partial base sequence redundancies and the mechanism of recombination is also discussed.