Within the human ERBB-2 gene promoter, a 100-base pair region 5' to the TATA box enhances basal transcription 200-fold. Two palindromes present within this 100-base pair region are important for transcription. The palindrome binding protein was purified to homogeneity and found to be identical to RBPJkappa, the mammalian homolog of Drosophila Suppressor of Hairless (Su(H)). Recombinant RBPJkappa bound the ERBB-2 promoter with affinity comparable with that seen with well characterized RBPJkappa binding sites. RBPJkappa activated an ERBB-2 palindrome-containing promoter in 293 cells. Because in Drosophila Su(H) acts downstream of NOTCH and because NOTCH.Su(H)/RBPJkappa stimulates transcription from target promoters, NOTCH-IC, a constitutively active form of NOTCH, was tested for effects on the ERBB-2 palindrome. NOTCH-IC further increased RBPJkappa-mediated transcription on wild type but not mutant ERBB-2 palindrome. Thus, RBPJkappa can activate ERBB-2 transcription and serve as an anchor to mediate NOTCH function on the ERBB-2 gene.