Metacyclic VSG expression site promoters are recognized by the same general transcription factor that is required for RNA polymerase I transcription of bloodstream expression sites.
Infectious metacyclic Trypanosoma brucei cells develop in the salivary glands of tsetse flies. A critical aspect of the developmental program leading to acquisition of infectivity is the synthesis of a variant surface glycoprotein (VSG) coat. Metacyclic VSG genes are transcribed from a set of specialized VSG expression sites (ESs) that differ from bloodstream VSG ESs by being monocistronic, being significantly shorter, lacking long stretches of 70-bp repeats, and having distinct promoter sequences. Both metacyclic and bloodstream VSG ESs are transcribed by the multifunctional T. brucei RNA polymerase I (Pol I), however the factor that recognizes the divergent metacyclic VSG ES promoters and recruits Pol I during the development to infectious cells remains unknown. We used an in vitro assay to show that the promoters for both metacyclic and bloodstream VSG ESs are recognized by the same class I transcription factor A (CITFA). This general Pol I transcription initiation factor was previously shown to be essential for the transcription of bloodstream VSG genes, procyclin genes and rRNA genes, and was demonstrated to have distinct binding affinities for these three types of promoters. We now show that differences in the sequence of individual metacyclic VSG ESs promoters determine different affinities for CITFA.
['Kolev|Nikolay G|NG|', 'Günzl|Arthur|A|', 'Tschudi|Christian|C|']
D001483:Base Sequence D001665:Binding Sites D005786:Gene Expression Regulation D009154:Mutation D059372:Nucleotide Motifs D011401:Promoter Regions, Genetic D011485:Protein Binding D012318:RNA Polymerase I D014157:Transcription Factors D014158:Transcription, Genetic D014346:Trypanosoma brucei brucei D014643:Variant Surface Glycoproteins, Trypanosoma
Metacyclics VSG Transcription Trypanosoma brucei Pol I CITFA