ABSTRACT
The promoters for chicken transforming growth factor-β2 (TGF-β2) and TGF-β3 were cloned and sequenced to study the regulation of these genes. The promoters are GC-rich and lie within CpG islands. Several putative DNA regulatory sequence motifs were identified in the 5′-flanking regions, including matches to particular recognition sequences for several nuclear factors found in other genes. A comparison of chicken and human TGF-β2 promoters revealed a 111 bp conserved sequence surrounding the major transcription start site. Two regions of sequence homology were detected in the 5′-flanking regions of chicken and human TGF-β3 genes: an 86 bp sequence surrounding the major transcription start and a 156 bp sequence in the 5′-untranslated region. No DNA sequence homology was detected between TGF-β1, -β2 or -β3 promoters. The conserved region near the major transcription start sites in both the TGF-β2 and TGF-β3 genes, however, does show some structural homology; both promoters contain short conserved sequences that resemble TATA box, cyclic AMP-responsive element and AP-2 sequence motifs, cis-acting elements we believe may be important for promoter activity.
