Specific interactions with TBP and TFIIB in vitro suggest that 14-3-3 proteins may participate in the regulation of transcription when part of a DNA binding complex

The 14-3-3 family of multifunctional proteins is highly conserved among ani mals, plants, and yeast. Several studies have shown that these proteins are associated with a G-box DNA binding complex and are present in the nucleus in several plant and animal species. In this study, 14-3-3 proteins are sh own to bind the TATA box binding protein (TBP), transcription factor IIB (T FIIB), and the human TBP-associated factor hTAF(II)32 in vitro but not hTAF (II)55. The interactions with TBP and TFIIB were highly specific, requiring amino acid residues in the box 1 domain of the 14-3-3 protein. These inter actions do not require formation of the 14-3-3 dimer and are not dependent on known 14-3-3 recognition motifs containing phosphoserine. The 14-3-3-TFI IB interaction appears to occur within the same domain of TFIIB that binds the human herpes simplex virus transcriptional activator VP16, because VP16 and 14-3-3 were able to compete for interaction with TFIIB in vitro. In a plant transient expression system, 14-3-3 was able to activate GAL4-depende nt beta-glucuronidase reporter gene expression at low levels when translati onally fused with the GAL4 DNA binding domain. The in vitro binding with ge neral transcription factors TBP and TFIIB together with its nuclear locatio n provide evidence supporting a role for 14-3-3 proteins as transcriptional activators or coactivators when part of a DNA binding complex.