Functional analysis of human interferon-beta gene transcriptional regulatory elements

One of the main goals of this project was to systematically evaluate the virus-inducible properties of the individual human interferon-beta (IFN-$ beta$) enhansons. Synthetic oligonucleotides representing the different enhansons were subcloned into an enhancerless SV$ sb1$CAT vector; the hybrid plasmids obtained were tested in different human cell lines by transient expression assay. The P2 motif, which is 80% homologous to the NF-$ kappa$B recognition sequence, was inducible by Sendai virus. In contrast, the P1 enhanson was transcriptionally silent. Unexpectedly, a multimer of the P5 motif conferred significant virus inducibility to a heterologous transcription unit. A DNA fragment encompassing P5, P1, and P2 mimicked the transcriptional activity of the whole IFN-$ beta$ promoter, indicating that the three enhansons act synergistically to confer a virus-inducible expression pattern. The effect of certain trans-acting factors on the individual IFN-$ beta$ enhansons was also assessed. Together, these experiments indicate that the synergism between the P5, P1, and P2 enhansons is mediated by at least two distinct transcription factors, NF-$ kappa$B and IRF-1