Characterization of the Variable Antigen Genes Expressed by Trypanosoma brucei rhodesiense during Metacyclic State and in Bloodstream

摘要

The objective of the research was to identify, clone and characterize the genes that code for the variant surface glycoproteins (VSGs) expressed during the metacyclic stage of the life cycle of the human pathogen, Trypanosoma rhodesiense. The genes and cDNAs for several such metacyclic VSGs were cloned, sequenced and used as the basis for a detailed examination of the molecular mechanisms regulating the expression of these genes. In contrast to many bloodstream VSG genes, it was found that metacyclic VSG genes do not undergo DNA rearrangement prior to their transcription but remain at their telomere-linked locations and are activated in situ. Specific sequences occur near their putative promoter sites that likely confer the stage-specific expression of these genes. During the course of this work, we also discovered that mung bean nuclease can be used to generate genomic DNA libraries containing these telomere-linked VSG genes. In addition, we demonstrated that a unique spliced leader sequence is common to all trypanosome mRNAs, including the VSG mRNs, and determined the sequences of two kinetoplast DNA minicircles. Keywords: Sleeping sickness. (AW)