- The trans-activator tax of human T-cell leukemia virus type 1 (HTLV-1) interacts with cAMP-responsive element (CRE) binding and CRE modulator proteins that bind to the 21-base-pair enhancer of HTLV-1. Suzuki, T., Fujisawa, J.I., Toita, M., Yoshida, M. Proc. Natl. Acad. Sci. U.S.A. (1993)