EMBL-CRG Systems Biology Unit, CRG-Centre de Regulacio Genomica, Dr Aiguader 88, 08003 Barcelona, Spain. christina.kiel@crg.es|EMBL-CRG Systems Biology Unit, CRG-Centre de Regulacio Genomica, Dr Aiguader 88, 08003 Barcelona, Spain. christina.kiel@crg.es