Transcriptional activators in yeast

Eukaryotic transcription activation domains (ADs) are not well defined on the proteome scale. We sys-tematicallly tested 6000 yeast proteins for trans-criptional activity using a yeast one-hybrid system and identified 451 transcriptional activators. We then determined their transcription activation strength using fusions to the Gal4 DNA-binding domain and a His3 reporter gene which contained a promoter with a Gal4-binding site. Among the 132 strongest activators 32 are known transcription factors while another 35 have no known function. Although zinc fingers, helix–loop–helix domains and several other domains are highly overrepresen-ted among the activators, only few contain character-ized ADs. We also found some striking correlations: the stronger the activation activity, the more acidic, glutamine-rich, proline-rich or asparagine-rich the activators were. About 29 % of the activators have been found previously to specifically interact with the transcription machinery, while 10 % are known to be components of transcription regulatory com-plexes. Based on their transcriptional activity, localization and interaction patterns, at least six previously uncharacterized proteins are suggested to be bona fide transcriptional regulators (namel