Activation of FUSE, the far upstream element, is required for the proper ex-pression of the mammalian gene c-Myc in undifferentiated cells. The binding of FBP1 (FUSE-binding protein or far upstream element-binding protein) to FUSE is necessary for c-Myc expression, indicating that FBP1 functions as a growth-dependent regulator of c-Myc expression. Isolated from proliferating HL-60 cells, FBP1 (FBP), FBP2 and FBP3 comprise a family of single-stranded DNA-binding proteins that specifically bind to FUSE elements. The FBP transcription factors share a conserved central DNA-binding domain and show significant homology in their carboxyl-terminal activation domains. Expression of FBP1 is detected in undifferentiated cells and is substantially decreased following cellular differentiation.
