Gene expression plays a pivotal role in the development of eukaryotic cells and their response to the environment. Failure to precisely program cellular gene expression often has pathological or deleterious consequences. Expression of most genes is initiated by the concerted action of transcription activators and coactivators that exhibit potent intrinsic activities to recruit RNA Polymerase II. While necessary for gene expression, this potent transcriptional activity poses a threat to the cell, as excessive gene transcription may lead to genome instability. Therefore, eukaryotic cells tightly control the deployment of (co)activator activities, but how this is achieved is largely unknown.
We study regulatory mechanisms that control transcription in the plant immune response. Plant immune responses are largely orchestrated by the immune hormone, salicylic acid (SA), which induces the reprogramming of thousands of genes to prioritize immune responses over normal cellular growth functions. SA-induced transcription reprogramming is largely mediated by NPR1, a master coactivator of gene expression. We recently reported that direct perception of SA by a Cullin3-RING ubiquitin ligase (CRL3) in the nucleus regulates the transcriptional activity of NPR1 by targeting it for degradation via the ubiquitin proteasome system. I will discuss our latest data suggesting that ubiquitination by CRL3 and other ubiquitin chain modifying enzymes may establish a processive ubiquitin timer and amplifier for transcriptional activity of NPR1.
URL : http://spoel.bio.ed.ac.uk