Retinoblastoma protein–E2F transcription factor complex (RB-E2F)

The Retinoblastoma protein–E2F transcription factor complex is a master regulator of the mammalian cell cycle, specifically controlling the transition from the G1 to the S phase (UniProt P06400). In its active, hypophosphorylated state, the Retinoblastoma protein (pRb) binds to E2F transcription factors, recruiting chromatin-remodeling factors to repress the expression of genes necessary for DNA synthesis (NIH PMC6162423). This interaction serves as a critical checkpoint; when pRb is phosphorylated by Cyclin-dependent kinases (CDK4/6), it undergoes a conformational change that releases E2F, allowing the cell to proceed with division (StatPearls NBK544313). Dysregulation of this complex is nearly universal in human cancers, often occurring through RB1 gene deletion, CDK4/6 overexpression, or loss of endogenous inhibitors like p16INK4a (Wikipedia: Retinoblastoma protein). Therapeutic strategies primarily focus on maintaining the RB-E2F complex in its bound state using CDK4/6 inhibitors, such as Palbociclib and Ribociclib, to induce cell cycle arrest in tumor cells (PubMed PMC5519112). However, the loss of functional RB1 protein is a common mechanism of resistance to these therapies, as the absence of pRb renders E2F permanently active regardless of kinase inhibition.

Other names

pRb-E2F complexRB1-E2F complexRetinoblastoma-associated protein 1-E2F complexRB-E2F1 complex

Stabilization of the hypophosphorylated RB-E2F complex via inhibition of Cyclin-dependent kinases 4 and 6 (CDK4/6), which prevents the release of E2F and subsequent transcription of S-phase genes.