Identification of a nuclear DNA binding protein associated with the interferon-beta upstream regulatory region

Nuclear protein extracts were prepared from uninduced myeloid leukemic KG-1 cells and analyzed for interferon-specific DNA binding by a gel electrophoresis DNA binding assay. A protein was detected that bound specifically to a 163-base pair upstream region of the IFN-beta promoter. A series of competition studies were performed to assess whether this was a general DNA binding protein; binding of this factor was competed from radiolabeled beta 163 fragment only by an excess of cold unlabeled beta 163 or a 67-base pair fragment (beta 67) derived from beta 163. Other promoter and enhancer transcriptional domains including 1) c-fos serum responsive element, 2) c-fos promoter, 3) SV40 enhancer, 4) IFN-alpha 1 promoter, and 5) plasmid pAT153 did not compete effectively for binding of the protein. These results indicate that this protein is not a general enhancer or promoter binding factor and may be unique to IFN-beta. Analysis of beta 67 DNA sequences revealed no homology to known recognition sequences for Sp1 or CTF transcription factors.