1. Wellcome Trust Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
2. Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
3. Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
4. Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA.