Non-B-DNA structures on the interferon-beta promoter?

The high mobility group (HMG) I protein intervenes as an essential factor d uring the virus induced expression of the interferon-beta (IFN-beta) gene. It is a non-histone chromatine associated protein that has the dual capacit y of binding to a non-B-DNA structure such as cruciform-DNA as well as to A T rich B-DNA sequences. In this work we compare the binding affinity of HMG I for a synthetic cruciform-DNA to its binding affinity for the HMGI-bindin g-site present in the positive regulatory domain II (PRDII) of the IFN-beta promoter. Using gel retardation experiments. we show that HMGI protein bin ds with at least ten times more affinity to the synthetic cruciform-DNA str ucture than to the PRDII B-DNA sequence. DNA hairpin sequences are present in both the human and the murine PRDII-DNAs. We discuss in this work the pr esence of, yet putative, non-B-DNA structures in the IFN-beta promoter. (C) Societe francaise de biochimie et biologie moleculaire/Elsevier, Paris.