Giardia lamblia TBP and BRF basal factors

ANDREA TROCHINE; HUGO DANIEL LUJAN; ESTEBAN SERRA

Misiones - Argentina

Congreso; VII Congreso Argentino de Protozoología y Enfermedades Parasitarias; 2004

Soc. Argentina de Investigacion Bioquimica y Biologia MOlecular

The TATA binding protein is an initiation factor that participates in the transcription together with the three eucaryotic RNA polymerases. Other initiation factors are also necessary for the polymerases to bind promoter sequences, among them is the TFIIB-related BRF,  wich acts in the ARN pol III dependent transcription. Exhaustive searches in the available genomic sequences of G.lamblia allowed us the identification of genes corresponding to orthologs of the eukaryotic factors TBP and BRF. Northern blot experiments showed that both transcripts are present in the parasites, with a higher expression on trophozoites than during the induction of encystment. Electrophoretic mobility shift assays performed with the recombinant proteins and different probes showed that both factors can bind double stranded DNA without an apparent sequence specificity. GIBRF heparin-resistant DNA-binding could be associated with a criptic DAN-binding site described at the C-terminus region of yeast BRF. Two hybrid experiment demonstrated that these factors interact with each other. Using this methodology, we also defined which domains are involved in the binding. DNA-protein and protein-protein interactions involving glTBP and glBRF represent the first experimental data that contributes to the understanding of the divergent mechanisms of transcription initiation regulation in Giardia lamblia.