Activating transcription factor 1 (ATF-1) is a protein that binds the cAMP response element (CRE) (consensus: 5'-GTGACGT[AC][AG]-3'), a sequence present in many viral and cellular promoters. ATF-1 binds to the Tax-responsive element (TRE) of HTLV-I. ATF-1 mediates PKA-induced stimulation of CRE-reporter genes. Defects in ATF-1 are linked to angiomatoid fibrous histiocytoma (AFH). AFH is a distinct variant of malignant fibrous histiocytoma that typically occurs in children and adolescents and is manifest by nodular subcutaneous growth.