Structural basis for reactivating the mutant TERT promoter by cooperative binding of p52 and ETS1

Abstract

Transcriptional factors ETS1/2 and p52 synergize downstream of non-canonical NF-?B signaling to drive reactivation of the ?146C>T mutant TERT promoter in multiple cancer types, but the mechanism underlying this cooperativity remains unknown. Here we report the crystal structure of a ternary p52/ETS1/?146C>T TERT promoter complex. While p52 needs to associate with consensus ?B sites on the DNA to function during non-canonical NF-?B signaling, we show that p52 can activate the ?146C>T TERT promoter without binding DNA. Instead, p52 interacts with ETS1 to form a heterotetramer, counteracting autoinhibition of ETS1. Analogous to observations with the GABPA/GABPB heterotetramer, the native flanking ETS motifs are required for sustained activation of the ?146C>T TERT promoter by the p52/ETS1 heterotetramer. These observations provide a unifying mechanism for transcriptional activation by GABP and ETS1, and suggest that genome-wide targets of non-canonical NF-?B signaling are not limited to those driven by consensus ?B sequences. © 2018, The Author(s).