Transcriptional transactivation by selected short random peptides attached to lexA-GFP fusion proteins

We performed a deliberate search of random peptide libraries for peptides capable of conferring transcriptional transactivation on the lexA DNA binding domain. Two libraries, one composed of C-terminal fusions, the other of peptide insertions within the green fluorescent protein structure, were used. We show that (i) peptide sequences other than C-terminal fusions can confer transactivation; (ii) though acidic activator peptides are more common, charge neutral and basic peptides can function as activators; and (iii) peptides as short as 11 amino acids behave in a modular fashion.These results support the recruitment model of transcriptional activation and, combined with other studies, suggest the possibility of using activator peptides in a variety of applications, including drug development work.Transcriptional activation is one of the key elements of eukaryotic gene expression. A variety of genetic, biochemical, and structural studies have revealed many mechanistic details of this process [see, for review, [1-3]]. In some cases, the structural/chemical basis for protein/DNA complex formation and recruitment of ancillary factors that promote transcription have been elucidated. Mutational analysis has defined regions of transcription factors – even specific residues – that participate in the activation process [4-9]. One of the most common structural features is the acidic activation domain, a region with excess negative charge present on many native activators as well as artificial ones. These activation domains are modular and can be effective when removed from one context and transplanted onto other DNA binding molecules [10,11].The yeast two-hybrid system exploits this modular feature of transcriptional activators [12,13]. Several variants of this general approach have been devised that employ DNA-binding domain and activation domain fusion proteins to assess and/or recover proteins that interact. The exceptional flexibility and efficiency of this system propell