par Pays, Etienne 
Référence Progress in nucleic acid research and molecular biology, 32, page (1-26)
Publication Publié, 1985
Référence Progress in nucleic acid research and molecular biology, 32, page (1-26)
Publication Publié, 1985
Article révisé par les pairs
| Résumé : | This chapter discusses gene conversion in African trypunosome antigenic variation. Antigenic variation allows African trypanosomes' to escape the immune defenses of their hosts. This occurs through differential surface antigen gene activation, with only one antigen gene being expressed at any one time among a large repertoire of different sequences. The differential gene activation can be achieved by gene conversion among antigen-specific sequences, taking place in a telomeric gene expression site. The analysis of several gene conversion endpoints and comparison with the mechanism for mating type interconversion in yeast suggests that the process could be triggered by a cut upstream from the antigen gene and then resolved by a crossing-over in a region of homology downstream from this point. This crossing-over could take place anywhere within the regions of homology, but only the recombinations leading to the successful generation of new antigen-coding sequences would be selected. Based on this gene conversion model, it is possible to explain the generation of mini-chromosomes harboring antigen-specific sequences. Translocation of such haploid telomeric sequences to the other end of other chromosomes would lead to the internalization of formerly telomeric genes and a clustering of haploid antigen-specific sequences near the chromosome termini. Studies show that the orientation of the conversion could be determined by the chromatin structure around the antigen gene. © 1985, Elsevier Inc. All rights reserved. |
