Protein deltex-1 is a protein that in humans is encoded by the DTX1 gene. Studies in Drosophila have identified this gene as encoding a positive regulator of the Notch-signaling pathway. The human gene encodes a protein of unknown function; however, it may play a role in basic helix-loop-helix transcription factor activity. DTX1 has been shown to interact with EP300. Functions as an ubiquitin ligase protein in vivo, mediating ubiquitination and promoting degradation of MEKK1, suggesting that it may regulate the Notch pathway via some ubiquitin ligase activity.