Catfish Oct2 binding affinity and functional preference for octamer motifs, and interaction with OBF-1

The DNA-binding (POU) domain of the catfish Oct2 transcription factor was s hown, by electromobility shift assays and surface plasmon resonance techniq ues, to have an affinity for the consensus octamer motif (ATGCAAAT) that wa s slightly higher than its affinity for a variant motif (ATGtAAAT). This ob servation is consistent with the transcriptional activation potentials of c atfish Oct2 alpha and Oct2 beta, which were shown to activate transcription in catfish B and T cell lines to an equivalent extent from both the consen sus and variant octamer motifs. When tested in a mouse plasmacytoma cell li ne, catfish Oct2 alpha and Oct2 beta, as well as mouse Oct2, showed higher transcriptional activation with the variant, as compared to the consensus, octamer motif. Catfish Oct2 was shown to function synergistically; with the mammalian co-activator, OBF-1, activating octamer-dependent transcription in catfish T cells. The strong transcriptional activity of OBF-1 in catfish cells was dependent on the presence of octamer motif(s) at the proximal (p romoter) rather than the distal (enhancer) position. (C) 1999 Elsevier Scie nce Ltd. All rights reserved.