PathwayStep4550 Activation of E2F target genes at G1/S G1/S-Specific Transcription GENE ONTOLOGYGO:0000083 Reactome Database ID Release 4369205 Reactome, http://www.reactome.org ReactomeREACT_683 The E2F family of transcription factors regulate the transition from the G1 to the S phase in the cell cycle. E2F activity is regulated by members of the retinoblastoma protein (pRb) family, resulting in the tight control of the expression of E2F-responsive genes. Phosphorylation of pRb by cyclin D:CDK complexes releases pRb from E2F, inducing E2F-targeted genes such as cyclin E.