Interferon-γ (IFN-γ) is an important immunoregulatory protein that is expressed usually only in large granular lymphocytes and T cells. The gene encoding IFN-γ was previously found to contain an intronic enhancer element that was not tissue-specific in its activity, despite the restricted expression of the intact IFN-γ-encoding gene. Using nuclear extracts from the human T-cell line Jurkat, we have now identified two protein-binding regions in this intronic enhancer element. One of the protected regions has strong partial identity to the NF-κB site present in the promoter region of the human interleukin 2-encoding gene. Based on this observation and recent reports of the interaction of the c-rel protooncogene product (c-Rel) with NF-κB sites, we determined whether c-Rel could interact with the intronic enhancer element in the human IFN-γ genomic DNA. Most surprisingly, gel-shift analysis, using c-Rel expressed in Escherichia coli established that c-Rel binds specifically to the IFN-γ intronic DNA but not to the interleukin 2-like NF-κB site. Additional studies with antibodies prepared against c-Rel peptides verified specificity of the interaction of c-Rel with this binding site. In addition, using an affinity-purified p50 subunit of the NF-κB complex, we observed that the p50 protein did not bind to this additional c-Rel-binding site. Furthermore, nucleotide sequence analysis of this DNA region revealed a strong similarity of the additional c-Rel-binding site to a previously identified IFN-stimulable response element. These data show that c-Rel can interact with DNA regions distinct from that recognized by NF-κB and may, in fact, be involved in transcriptional regulation of the IFN-stimulable genes via the IFN-stimulable response element.
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - 1992|
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