INTRINSICALLY BENT DNA IN A EUKARYOTIC TRANSCRIPTION FACTOR RECOGNITION SEQUENCE POTENTIATES TRANSCRIPTION ACTIVATION

Many eukaryotic transcription factors induce DNA bending on binding to their recognition sequences. DNA bending could play a structural role by altering contacts between the protein and DNA. Alternatively, DNA bending could play a more direct role in transcription activation. To distinguish between these possibilities, we inserted two to eight copi es of the intrinsic bending sequence, AAAAAACGTG, into a minimal promo ter containing only a TATA box. The intrinsic DNA bending sequence was a potent activator of transcription in both in vivo transfection expe riments and in a cell-free transcription system. A protein binds to th e intrinsic bending sequence with high specificity in gel mobility shi ft assays and was required for its transcription in cell-free extracts , The intercalator, distamycin, which eliminates the ability of the se quence to bend, specifically reduced its transcription by about 60%. M utations in the sequence which abolished DNA bending reduced transcrip tion by approximately 70% in vivo. Competition gel mobility shift assa ys showed that the transcription factor bound equally well to mutants in which DNA bending was abolished and to the intrinsic bending sequen ce. These data indicate that DNA bending can play a direct role in the activation of eukaryotic transcription.