Trypanosoma cruzi TBP shows preference for C/G-rich DNA sequences in vitro

Recent findings associate transcription start in trypanosomatids with chromatin regions containing modified and variant histones. TATA-binding protein (TBP) and other fundamental transcription factors have been also found at these Transcription Start Sites (TSS). Results of Systematic Evolution of Ligands by Exponential Enrichment (SELEX) experiments show that Trypanosoma cruzi TBP (TcTBP) has an in vitro binding preference for G-rich sequences. This finding correlates with the presence of G-rich stretches at the Strand Switch Regions (SSR) and at some putative internal TSS in Trypanosoma brucei and Leishmania. A scanning study of partially assembled T. cruzi genomic contigs determined the presence of G-rich stretches in the coding strands. TcTBP affinity for G-rich sequences suggests that this factor could play a role in locating the initiation complex in the right TSS, probably by "sensing" the G-content on the strand to be transcribed.