Activation domains, of transcription factors

No common structural motifs are known for the activation domains of transcription factors. Activation domains that are rich in acidic amino acids, glutamines or prolines have been reported. 

The activation domains of transcription factors generally recruit other proteins that promote transcription. Some of these activation domains interact directly with RNA polymerase II. In other cases, an activation domain may... 

Protein-protein interactions are studied, for example, by the yeast two-hybrid-system, a genetic technique designed to identify novel protein-protein interactions that were previously detected by biochemical studies. All two-hybrid screening systems rely on the fact that transcriptional activation and DNA-binding domains of transcription factors are modular in nature. In these systems, the coding sequence for the DNA-binding domain of a transcription factor such as Gal4 or LexA is fused to the cDNA of a protein of interest, termed... 

Yamamoto KK, Gonzales GA, Biggs WH, Montminy MR. Characterization of a bipartite activator domain in transcription factor CREB. Nature 1988 334 494 98. 

Activator Protein-1 (API) comprises transcriptional complexes formed by dimers of members oftheFos, Jun, and ATF family of transcription factors. These proteins contain basic leucine zipper domains that mediate DNA binding and dimerization. They regulate many aspects of cell physiology in response to environmental changes. 

While activation of HSFl and HSF2 results in the increased expression of HS genes, recent studies indicate that there are distinct differences between these transcription factors. As noted previously, HSFl is the heat-inducible form of the HS factors, whereas HSF2 is activated by hemin (Sistonen et al., 1992). This observation has indicated a possible role of HSF2 in cellular differentiation. It also indicates that the activation domains of the two transcription factors are quite different. Presumably the DNA binding properties of the two transcription factors are similar, but recent experiments indicate otherwise (Kroger and Morimoto,... 

FIGURE 8.12 Direct phosphorylation of the STAT class of transcription factors. Through their SH2 domains, the p84Slalla and p91StaIlb associate with the receptor and become phosphorylated on tyrosine residues. They form a dimer (called the Sis-inducible factor, or SIF) that translocates to the nucleus, where it binds to a Sis-inducible element (SIE) and activates transcription of, for example, the c-fos gene. 

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