Component of a transcriptional repressor complex together with MAX (PubMed:8425218). In complex with MAX binds to the core DNA sequence 5'-CAC[GA]TG-3' (PubMed:8425218). Antagonizes MYC transcriptional activity by competing with MYC for MAX binding (PubMed:8425218). Binds to the TERT promoter and represses telomerase expression, possibly by interfering with MYC binding (PubMed:12837246).