Genomic organization and promoter function of the murine tumor necrosis factor receptor beta gene

Using the tumor necrosis factor receptor beta (TNFR beta) cDNA as a probe, overlapping clones from a genomic phage library were isolated which encompass the murine TNF receptor beta gene. Analysis of the gene led to the identification of 10 exons, most of which were concentrated in two clusters. The boundaries of the exons do not match protein domains or characteristic motifs of the extracellular region of the TNFR beta. The 5'-flanking region of the gene shows a high density of G and C nucleotides with a strong overrepresentation of CpG dinucleotides. Most of the analyzed CpG were found to be nonmethylated, suggesting that this region is an HTF island. We revealed at least three transcriptional start sites which is likely due to the absence of classical TATA and CAAT sequences from the putative promoter region. CAT assays confirmed promoter activity of the 5'-flanking sequences. Surprisingly, some successively shortened promoter constructs displayed higher relative promoter activity than a full length clone. Preliminary experiments indicate that the promoter region of the TNFR beta gene does not respond to a variety of cytokines. In summary, the structural and functional analysis suggest that the TNFR beta expression is directed by a non-inducible housekeeping-type promoter.