CREB1 and leukemia: Tax immortalizes T lymphocytes and induces leukemia in transgenic mice.148,149 It promotes viral transcription from a promoter located within the long terminal repeat (LTR).150,151,152 The N-terminus of Tax (Figure 4A) directly binds to CREB to form a ternary complex of TRE–Tax–CREB (Tax-responsive element–Tax–CREB) within the viral promoter.154,155 Binding of Tax to CREB enhances CREB homodimerization, which strengthens its association with promoter DNA.156 TRE activation requires Tax homodimerization, which involves CREB homodimerization.