SYNERGISTIC ACTIVATION OF TRANSCRIPTION BY MULTIPLE BINDING-SITES FOR NF-KAPPA-B EVEN IN ABSENCE OF COOPERATIVE FACTOR BINDING TO DNA

Regulation of eukaryotic genes is largely governed by multiple cis-acting DNA sequences recognized by specific transcription factors. The transcription factor NF-κB has been implicated as an important regulator of cellular and viral genes, including those of immunoglobulin κ light chain, interleukin-2, β-interferon, HIV-1 and cytomegalovirus. We have analyzed the effect of increasing the number of NF-κB sites, located directly upstream from the TATA {ballot box}. Four copies of the sequence gave a more than 100-fold stimulation relative to a single copy, suggesting that NF-κB proteins act synergistically to bring about this dramatic increase in transcription. By DNase I footprinting we demonstrated factor binding to two adjacent NF-κB sites in vitro. However, we found no evidence for co-operative binding to these DNA sites. We propose that the high transcriptional activity results from another type of co-operation, based on multiple weak interactions of the NF-κB factors with another component of the transcription apparatus, perhaps RNA polymerase II itself. © 1990 Academic Press Limited.