1. Centre for Genomic Regulation (CRG) and Universitat Pompeu Fabra, Avenida Dr. Aiguader 88, 08003 Barcelona, Spain.
2. European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
3. Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow 127994, Russia.
4. Zentrum für Molekulare Biologie Heidelberg (ZMBH), Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
5. Institució Catalana de Recerca i Estudis Avançats, Lluis Companys 23, Barcelona 08010, Spain.