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VSG gene expression site control in insect form Trypanosoma brucei
G Rudenko1, P A Blundell, M C Taylor
1The Netherlands Cancer Institute, Amsterdam.
The EMBO Journal
|November 15, 1994
Summary
African trypanosomes switch coats in tsetse flies, stopping variant surface glycoprotein (VSG) gene transcription. Multiple VSG expression site promoters remain active in insect forms, influenced by DNA sequence and genomic location.
Area of Science:
- Molecular biology
- Parasitology
- Genetics
Background:
- African trypanosomes (Trypanosoma brucei) change their surface coat from variant surface glycoprotein (VSG) to procyclin upon entering tsetse flies.
- VSG gene transcription ceases in the fly, but promoter activity persists.
- The regulation of these active promoters (single high-activity vs. multiple low-activity) was previously unclear.
Purpose of the Study:
- To determine if one or multiple VSG expression site promoters are active in insect-form trypanosomes.
- To investigate the factors influencing the down-regulation of VSG gene expression site promoters.
Main Methods:
- Utilized sequence variations between different VSG expression sites to distinguish promoter activity.
- Introduced single-copy marker genes into transcribed regions to assess expression levels.
- Experimentally relocated VSG expression site promoters to ribosomal DNA (rDNA) loci.
- Replaced endogenous VSG expression site promoters with rDNA promoters.
Main Results:
- Demonstrated that multiple VSG expression site promoters are active in insect-form trypanosomes.
- Confirmed promoter activity through low expression of introduced marker genes.
- Showed promoter derepression when relocated to rDNA loci.
- Observed derepression upon replacement with rDNA promoters.
Conclusions:
- The down-regulation of VSG gene expression site promoters in insect-form trypanosomes is a complex process.
- Both the intrinsic DNA sequence of the promoter and its surrounding genomic context significantly influence promoter activity.