Activation of yeast RNA polymerase II transcription by a thymidine-rich upstream element in vitro

A thymidine-rich sequence upstream of the DED1 gene of Saccharomyces cerevisiae activated transcription of the CYC1 promoter by RNA polymerase II in vitro. Activation was inhibited by an excess of an oligonucleotide with the same but not a closely related thymidine-rich sequence, pointing to the involvement of a specific thymidine-rich element-binding factor. The extent of activation was as great as 30-fold and showed a similar distance and orientation dependence and a similar effect of deletions in vitro as in vivo.