TY - JOUR T1 - Maximal Aryl Hydrocarbon Receptor Activity Depends on an Interaction with the Retinoblastoma Protein JF - Molecular Pharmacology JO - Mol Pharmacol SP - 664 LP - 673 DO - 10.1124/mol.59.4.664 VL - 59 IS - 4 AU - Cornelis J. Elferink AU - Nie-Lin Ge AU - Aviva Levine Y1 - 2001/04/01 UR - http://molpharm.aspetjournals.org/content/59/4/664.abstract N2 - The aryl hydrocarbon receptor (AhR) belongs to the basic helix-loop-helix/periodicity/AhR nuclear translocator/simple-minded (Per-Arnt-Sim) family of transcription factors that regulate critical functions during development and tissue homeostasis. Within this family, the AhR is the only member conditionally activated in response to ligand binding, typified by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We recently demonstrated that the AhR interacts with the retinoblastoma protein (pRb). This report presents evidence that a LXCXE motif in the AhR protein confers pRb binding, which is necessary for maximal TCDD induced G1 arrest in rat 5L hepatoma cells. The data support a mechanism whereby pRb seems to regulate G1 cell cycle progression distinct from the direct repression of E2F-mediated transcription. Furthermore, the results indicate that the AhR-pRb interaction regulates TCDD induction of CYP1A1, suggesting that pRb may be a general AhR coactivator. ER -