1. Chromatin Structure and Mobile DNA, The Francis Crick Institute, London NW1 1AT, UK.
2. Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215, USA.
3. Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
4. Macromolecular Machines Laboratory, The Francis Crick Institute, London NW1 1AT, UK.
5. Institute for Experimental Pathology, University of Iceland, Keldur, 112 Reykjavik, Iceland.
6. Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK.
7. Macromolecular Structure Laboratory, The Francis Crick Institute, London NW1 1AT, UK.
8. Division of Medicine, Imperial College London, London W2 1PG, UK.