A novel telomeric gene conversion in Trypanosoma brucei. 1989

J K Scholler, and P J Myler, and K D Stuart
Seattle Biomedical Research Institute, WA 98109-1651.

Gene conversion is one mechanism of antigenic variation in Trypanosoma brucei. Variant surface glycoprotein (VSG) genes are duplicated by this process to telomeric locations from which they may be expressed. We examined four independent antigenic switches in which the IsTaR 1.1 minichromosomal VSG gene is duplicated to a large chromosome where it is expressed. An unusual feature of three of these telomeric gene conversions is that the distance between the VSG gene and the end of the chromosome is identical for both the basic and duplicated copies following the antigenic switch. This suggests that the gene conversion is initiated 5' to the VSG gene and extends to the end of the telomere. The data also suggest that events other than simple nucleotide addition account for telomeric growth.

UI MeSH Term Description Entries
D007621 Karyotyping Mapping of the KARYOTYPE of a cell. Karyotype Analysis Methods,Analysis Method, Karyotype,Analysis Methods, Karyotype,Karyotype Analysis Method,Karyotypings,Method, Karyotype Analysis,Methods, Karyotype Analysis
D002874 Chromosome Mapping Any method used for determining the location of and relative distances between genes on a chromosome. Gene Mapping,Linkage Mapping,Genome Mapping,Chromosome Mappings,Gene Mappings,Genome Mappings,Linkage Mappings,Mapping, Chromosome,Mapping, Gene,Mapping, Genome,Mapping, Linkage,Mappings, Chromosome,Mappings, Gene,Mappings, Genome,Mappings, Linkage
D004247 DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D004587 Electrophoresis, Agar Gel Electrophoresis in which agar or agarose gel is used as the diffusion medium. Electrophoresis, Agarose Gel,Agar Gel Electrophoresis,Agarose Gel Electrophoresis,Gel Electrophoresis, Agar,Gel Electrophoresis, Agarose
D005785 Gene Conversion The asymmetrical segregation of genes during replication which leads to the production of non-reciprocal recombinant strands and the apparent conversion of one allele into another. Thus, e.g., the meiotic products of an Aa individual may be AAAa or aaaA instead of AAaa, i.e., the A allele has been converted into the a allele or vice versa. Polar Recombination,Polaron,Conversion, Gene,Conversions, Gene,Gene Conversions,Polar Recombinations,Polarons,Recombination, Polar,Recombinations, Polar
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D000940 Antigenic Variation Change in the surface ANTIGEN of a microorganism. There are two different types. One is a phenomenon, especially associated with INFLUENZA VIRUSES, where they undergo spontaneous variation both as slow antigenic drift and sudden emergence of new strains (antigenic shift). The second type is when certain PARASITES, especially trypanosomes, PLASMODIUM, and BORRELIA, survive the immune response of the host by changing the surface coat (antigen switching). (From Herbert et al., The Dictionary of Immunology, 4th ed) Antigen Switching,Antigenic Diversity,Variation, Antigenic,Antigen Variation,Antigenic Switching,Antigenic Variability,Switching, Antigenic,Diversity, Antigenic,Switching, Antigen,Variability, Antigenic,Variation, Antigen
D000953 Antigens, Protozoan Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered. Protozoan Antigens
D014346 Trypanosoma brucei brucei A hemoflagellate subspecies of parasitic protozoa that causes nagana in domestic and game animals in Africa. It apparently does not infect humans. It is transmitted by bites of tsetse flies (Glossina). Trypanosoma brucei,Trypanosoma brucei bruceus,Trypanosoma bruceus,brucei brucei, Trypanosoma,brucei, Trypanosoma brucei,bruceus, Trypanosoma,bruceus, Trypanosoma brucei
D014643 Variant Surface Glycoproteins, Trypanosoma Glycoproteins attached to the surface coat of the trypanosome. Many of these glycoproteins show amino acid sequence diversity expressed as antigenic variations. This continuous development of antigenically distinct variants in the course of infection ensures that some trypanosomes always survive the development of immune response to propagate the infection. Surface Variant Glycoproteins, Trypanosoma,Trypanosoma Variant Surface Coat Glycoproteins,SSP-4,VSG 117,VSG 118,VSG 221

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