GSE130798
Identification of sequence-specific promoters driving polycistronic transcription initiation by RNA Polymerase II in trypanosomes
Protein coding genes in the trypanosome genome are organized in polycistronic transcription units (PTUs). How RNA Polymerase II (Pol II) initiates PTU transcription has not been resolved and the current model favors initiation driven by chromatin epigenetic marks, rather than core-promoters. Here, we identify sequence-specific core promoters by functional characterization of ChIP-Seq Pol II accumulation-peaks. Sequences located between oppositely orientated PTUs contained two independent and distinct core promoters, driving unidirectional transcription. Detailed analysis of one promoter identified 75 bp, necessary and sufficient to fully drive reporter expression, and containing short functional motifs. Analysis of further promoters suggested activity and initiation is regulated and both, focused and dispersed transcription patterns were found. Thus, in contrast to the model of unregulated and promoter-independent transcription initiation, sequence-specific promoters determine the initiation of RNA Pol II transcription of protein coding genes in trypanosomes. These findings resolve the discrepancy between trypanosomes and other eukaryotes in how Pol II initiates protein-coding gene transcription. Overall design: ChIP-Seq analysis of RNA pol II accumulation in Trypanosoma brucei brucei using anti-RPB1 antibodies and sequenced in Illumina NextSeq 500.