OCT PROTEINS ARE QUALITATIVE RATHER THAN QUANTITATIVE REGULATORS OF KAPPA-TRANSCRIPTION

The 3' flanking sequence of kappa promoter octamers was found to conta in either a conserved A or G residue which increased the affinity of t he octamer core motif for Oct1 and Oct2A. By transient transfections i t was shown that decreasing the affinity of an octamer for Oct binding was crippling the transcription unit when the octamer was used in a m inimal promoter, while it had only marginal effects when it was analys ed in the context of an intact kappa promoter. As the octamer in a kpr omoter was replaced by a TAATGARAT motif with equal affinity for Oct p rotein binding the latter could still participate in synergistic trans criptional stimulation. Thus, the synergistic interactions involved in kappa promoter transcriptional stimulation are dependent on the prese nce of Oct proteins but not on the octamer DNA motif per se. Since the transcriptional coactivator OCA-B cannot interact with Oct protein bo und to the TAATGARAT motif, the role of OCA-B in these interactions se ems to be limited. (C) 1997 Elsevier Science Ltd. All rights reserved.