BTBD6 (BTB/POZ domain-containing protein 6), also known as BDPL or lens BTB domain protein, is a 410 amino acid protein that contains one BTB/POZ domain and is specifically expressed in the lens. The BTB/POZ domain mediates homomeric and heteromeric POZ-POZ interactions and is common to transcriptional regulators involved in chromatin modeling. In several BTB/POZ containing proteins, including BCL-6 and the promyelocytic leukemia zinc-finger (PLZF) oncoprotein, this domain interacts with the SMRT/N-CoR-mSin3A HDAC complex and is directly involved in repressing and silencing gene transcription. When this domain is deleted, as with the oncogenic PLZF-RAR chimera of promyelocytic leukemias, this transcriptional repression is attenuated. This suggests that BTBD6 may play a role in transcription regulation in the lens.