A unique transactivation sequence motif is found in the carboxyl-terminal domain of the single-strand-binding protein FBP.
The far-upstream element-binding protein (FBP) is one of several recently described factors which bind to a single strand of DNA in the 5' region of the c-myc gene. Although cotransfection of FBP increases expression from a far-upstream element-bearing c-myc promoter reporter, the mechanism of this stimulation is heretofore unknown. Can a single-strand-binding protein function as a classical transactivator, or are these proteins restricted to stabilizing or altering the conformation of DNA in an architectural role? Using chimeric GAL4-FBP fusion proteins we have shown that the carboxyl-terminal region (residues 448 to 644) is a potent transcriptional activation domain. This region contains three copies of a unique amino acid sequence motif containing tyrosine diads. Analysis of deletion mutants demonstrated that a single tyrosine motif alone (residues 609 to 644) was capable of activating transcription. The activation property of the C-terminal domain is repressed by the N-terminal 107 amino acids of FBP. These results show that FBP contains a transactivation domain which can function alone, suggesting that FBP contributes directly to c-myc transcription while bound to a single-strand site. Furthermore, activation is mediated by a new motif which can be negatively regulated by a repression domain of FBP.
Duncan
R
R
Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland 20892, USA.
Collins
I
I
Tomonaga
T
T
Zhang
T
T
Levens
D
D
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D005656:Fungal Proteins / Q000096:biosynthesis; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D029701:Saccharomyces cerevisiae Proteins; D016385:TATA Box; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection; D014443:Tyrosine
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D014443:Tyrosine; D015500:Chloramphenicol O-Acetyltransferase