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