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Biomedical subjects

N A Lisitsyn

Publications and source records attributed to N A Lisitsyn.

13 recordsLinked to original sources
PubMed1995

Comparative genomic analysis of tumors: detection of DNA losses and amplification.

We demonstrate the use of representational difference analysis for cloning probes that detect DNA loss and amplification in tumors. Using DNA isolated from human tumor cell lines to drive hybridization against matched normal DNA, we were able to identify six genomic regions that are homozygously deleted in cultured cancer cells. When this method was applied in the reverse way, using normal DNA to drive hybridization against tumor cell DNA, we readily isolated probes detecting amplification. Representational difference analysis was also performed on DNAs derived from tumor biopsies, and we thereby discovered a probe detecting very frequent homozygous loss in colon cancer cell lines and located on chromosome 3p.

Animals↗
PubMed1994

Direct isolation of polymorphic markers linked to a trait by genetically directed representational difference analysis.

We describe a technique, genetically directed representational difference analysis (GDRDA), for specifically generating genetic markers linked to a trait of interest. GDRDA is applicable, in principle, to virtually any organism, because it requires neither prior knowledge of the chromosomal location of the gene controlling the trait nor the availability of a pre-existing genetic map. Based on a subtraction technique described recently called representational difference analysis, GDRDA uses the principles of transmission genetics to create appropriate Tester and Driver samples for subtraction. We demonstrate the usefulness of GDRDA by, for example, successfully targeting three polymorphisms to an interval of less than 1 cM of the mouse nude locus of chromosome 11.

Animals↗
PubMed1990

Isolation of rapidly evolving genomic sequences: construction of a differential library and identification of a human DNA fragment that does not hybridize to chimpanzee DNA.

A differential library enriched in rapidly evolving human genomic sequences was obtained by phenol-enhanced hybridization of human genomic DNA with an excess of chimpanzee DNA. A DNA fragment 110 bp in length that did not hybridize to either chimpanzee or other primate DNA was identified in this library. It was shown to be a substantially diverged member of the human beta satellite family of tandem repeats. The genomic sequences homologous to the fragment were located on the short arms of human acrocentric chromosomes by in situ hybridization. The human-specific fragment failed to hybridize with RNA from different human tissues. The human-specific fragment exhibits a remarkable level of DNA polymorphism in humans and may be used in the identification of human tissue samples, in the selection of human/rodent somatic cell hybrids containing human acrocentric chromosomes, and in the mapping of these chromosomes.

Animals↗
PubMed1988

Genes coding for RNA polymerase beta subunit in bacteria. Structure/function analysis.

The nucleotide sequence of the rpoB gene of Salmonella typhimurium has been determined in this work. It was compared with known sequences of the gene from other sources and the conservative regions were detected. This allowed some interesting conclusions to be made about the distribution of the functional domains in bacterial RNA polymerase and about the three-dimensional structure of its beta subunit.

Amino Acid Sequence↗
PubMed1985

[Localization of mutation leading to resistance of E. coli RNA polymerase to the antibiotic streptolydigin in the gene rpoB coding for the beta-subunit of the enzyme].

For the first time a mutation of streptolydigin resistance was localized. It was discovered to be a double substitution, namely Gly544----Asp, Phe545----Ser, in the region where most rif-r mutations are located. One may suppose that this region takes part in the formation of both elongation NTP binding site, blocked by streptolydigin, and RNA chain binding and translocation site that is blocked by rifampicin.

Aminoglycosides↗
PubMed1984

Mutation to rifampicin resistance at the beginning of the RNA polymerase beta subunit gene in Escherichia coli.

The unusual recombinant plasmid pRC19 carrying the N-terminal fragment of the Escherichia coli RNA polymerase rpoB gene was found to specify high level rifampicin resistance of E. coli cells. Sequence analysis of this plasmid revealed one substitution only: transversion G----T, leading to amino acid substitution Val146----Phe. This mutational change marks the second domain of the beta subunit involved in rifampicin binding.

Base Sequence↗
PubMed1984

[Nucleotide substitutions in the rpoB gene leading to rifampicin resistance of E. coli RNA polymerase].

Three new rif-r-mutations, obtained independently, were localized in the rpoB gene coding for the beta-subunit of DNA-dependent RNA polymerase of E. coli. Two of them led to identical Asp(516)-Asn amino acid substitution with relatively low resistance of corresponding E. coli strains to rifampicin. The third mutation affected the His 526 residue transforming it into Tyr and endowed the E. coli cells with a high resistance against rifampicin.

Base Sequence↗