Professor Ron Hay
| Position: | Professor of Molecular Biology |
|---|---|
| Address: | College of Life Sciences University of Dundee Dundee |
| Telephone: | +44 (0)1382 386309, internal ext. 86309 |
| Email: | r.t.hay@dundee.ac.uk |
| Links: | Hay Lab Website |
Research Overview
Role of ubiquitin and ubiquitin-like proteins in transcriptional regulation
Ubiquitin and ubiquitin-like proteins are covalently linked to target proteins. While polyubiquitinated proteins are destined to be degraded by the proteasome, modification by the ubiquitin-like proteins SUMO and NEDD8 are responsible for altering the function of target proteins. We have previously shown that the ubiquitin-like proteins have profound effects on gene expression and our objective is to define the function of these post-translational modifications in cellular metabolism. One of the transcription factors regulated by ubiquitin-like proteins is NF-kB. This transcription factor is an intracellular mediator of signals involved in the development of immune and inflammatory disease. NF-kB activity is controlled by ubiquitin-mediated proteasomal degradation of the inhibitor protein IkB that leads to increased expression of cytokine and viral genes. We showed that signal induced activation of NF-kB involved site-specific phosphorylation and ubiquitination of IkBa. Subsequently we demonstrated that IkBa was a shuttling protein that functioned by binding NF-kB and exporting the inactivated transcription factor out of the nucleus. The importance of this pathway was illustrated by our observation that the high level constitutive NF-kB activation that is the hallmark of Hodgkin's Lymphoma is a consequence of mutations in the gene for IkBa.
The objective of our work is to determine the mechanism of NF-kB activation and to identify inhibitors of the NF-kB pathway. To this end we are employing advanced proteomic approaches to identify proteins that interact with NF-kB under different physiological conditions. Functional analysis and RNAi mediated knock out of the interacting components will reveal their role in the control of NF-kB dependent transcription. To identify inhibitors of NF-kB activity we are employing high throughput screening of natural product libraries and have isolated new chemical entities that inhibit NF-kB. The site of action of these inhibitors will be determined and their role as anti-inflammatory agents assessed in vivo.
The ubiquitin-like protein SUMO-1 is an important regulator of cellular function. We cloned the genes required for SUMO conjugation and established that in the case of IkBa, SUMO modification and ubiquitination compete for the same lysine residue. The outcome of this competition determines whether IkBa is stabilsed or degraded. We demonstrated that a number of important transcription factors (p53, p300 and Elk-1) were modified with SUMO and that the modification altered their transcriptional activity. In the case of p300 we demonstrated that SUMO modification resulted in the recruitment of histone deacetylases that were responsible for chromatin modification and transcriptional repression. Recently we have used proteomics to identify hundreds of new SUMO substrates. From the list of modified proteins we have identified proteins with interesting properties and we will use these substrates to determine the role of SUMO modification in an in vivo setting.