The Structure of Eucaryotic Transcriptional activators

It is generally true that eucaryotic transcriptional activators act via direct or indirect protein-protein contacts with the transcription apparatus and/or chromatin components. In this context, the definition of the transcription apparatus is rather broad it includes the basal apparatus as well as proteins which act as coactivators or mediators. 

For a DNA-binding protein to engage in the regulation of activation of transcription it must possess the following functions  

In many cases the various functions are located on independently folding protein domains, resulting in modularly constructed transcriptional activators. 

Transcriptional activators bind specifically to cognate DNA elements variably located relative to the promotor and can interact directly or indirectly with the transcription apparatus. Transcriptional activators depend on the occurrence of regulatory DNA elements for their action and perform their function on specific genes. They are thus also termed specific transcriptional activators, in contrast to proteins called coactivators that activate transcription independently of specific DNA elements (see Section 1.4.4.2). 

The first data concerning the structural requirements for communication with the transcription apparatus came from domain-swapping experiments with the GAL4 protein of yeast. 

In many cases the various functions are located on independently folding protein domains, resulting in modularly constructed transcriptional activators. The function of a DNA-binding protein can thus often be deduced from the primary sequence information and from homology with other eucaryotic transcriptional activators. Furthermore, the modular structure of transcriptional activators is the prerequisite for the 

Examples for other trans-activating domains are the glutamine rich domains of the transcription factor Spl and the prohne rich domain of the transcription factor CTF/ NFl, which contains 20 % prohne residues. 

It is assumed that trans-activating domains are structural elements that can adapt to become complementary to a smface of the transcription apparatus in a flexible and rather rmspecific manner. Information on the structure of the trans-activating domain. 

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