(800-63) Good fences make good neighbors; the BORDER family of negative transcription elongation factors prevent transcriptional interference and repress gene expression in Arabidopsis
Professor and Chair Indiana Univeristy Bloomington, Indiana
Body of Abstract: Transcription initiation is a well-characterized regulatory step in gene expression, however, it is becoming clear that downstream events, such as transcription elongation are also important. Recent work in our lab has shown that the BORDER (BDR) family of negative transcription elongation factors play important roles in gene regulation in at least two distinct contexts. First, they help prevent transcriptional interference between neighboring genes. BDR proteins are enriched in intergenic regions of chromatin where they promote the 3’ pausing of RNA Polymerase II (Pol II). This is especially important in the case of closely spaced genes on the same DNA strand, where Pol II transcription must stop precisely at the 3’ end of the upstream gene, in order to not interfere with the promoter region of the downstream gene. In the absence of BORDER proteins, 3′ pausing associated with the upstream gene is reduced and Pol II shifts into the promoter region of the downstream gene, reducing its expression. Second, BDR proteins can repress gene expression by inhibiting the progression of Pol II. A well-characterized example of gene regulation via the inhibition of elongation is promoter-proximal pausing in animals, where transcriptionally engaged Pol II accumulates ~50 bp downstream of the transcription start site and is thought to facilitate subsequent rapid activation. Plants lack critical components of the machinery required for animal-like promoter proximal pausing, however, the BDR proteins may serve a similar role. Like paused genes in animals, BDR-repressed genes are characterized by high levels of Pol II occupancy in their repressed state, suggesting that these genes could be poised for rapid reactivation. Consistent with this model, BDR-repressed genes are enriched in defense genes, whose rapid activation may be advantageous.