THE FAR UPSTREAM ELEMENT-BINDING PROTEINS COMPRISE AN ANCIENT FAMILY OF SINGLE-STRAND DNA-BINDING TRANSACTIVATORS

The cloning and expression of two new human cDNAs encoding proteins hi ghly related to the far upstream element-binding protein (FBP) are des cribed, FBP, FBP2, and FBP3 comprise a family of single-strand DNA-bin ding proteins that possess all of the general features of more convent ional transcription factors. The FBPs each bind sequence specifically to only one strand of the far upstream element (FUSE; originally ident ified upstream of c-myc), and each possesses potent activation domains when fused to the GAL4 DNA-binding domain and assayed by transient tr ansfection. Typical of transcription factors, the proteins are most hi ghly related in their central, DNA-binding domains, but extensive homo logy is also shared within the tyrosine-rich, carboxyl-terminal activa tion domains. Comparison with Gen Bank sequences revealed a fourth FBP family member encoded by Caenorhabditis elegans chromosome III, illus trating the high degree of homology in this evolutionarily ancient and conserved family.