1. Departament de Genètica, Microbiologia i Estadística, Facultat de Biologia and Institut de Biomedicina (IBUB), Universitat de Barcelona , Barcelona , Catalonia , Spain
2. Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology (BIST) , Barcelona , Catalonia , Spain
3. German Cancer Research Center (DKFZ) Heidelberg, Division B140 , 69120 Heidelberg , Germany
4. Universitat Pompeu Fabra (UPF) , Barcelona , Catalonia , Spain