The cyclin-dependent kinase inhibitor p27 Kip1 interacts with the aryl hydrocarbon receptor and negatively regulates its transcriptional activity.

p27 Kip1 functions to coordinate cell cycle progression through the inhibition of cyclin-dependent kinase (CDK) complexes. p27 Kip1 also exerts distinct activities beyond CDK-inhibition, including functioning as a transcriptional regulator. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor with diverse biological roles. The regulatory inputs that control AhR-mediated transcriptional responses are an active area of investigation. AhR was previously established as a direct regulator of p27 Kip1 transcription. Here, we report the physical interaction of AhR and p27 Kip1 and show that p27 Kip1 expression negatively regulates AhR-mediated transcription. p27 Kip1 knockout cells display increased AhR nuclear localisation and significantly higher expression of AhR target genes. This work thus identifies new regulatory cross-talk between p27 Kip1 and AhR.