Structural organization and promoter activity of the human ryudocan gene

To better understand the regulation of ryudocan (syndecan-4) expression, we have determined the structural organization of the human ryudocan gene. The human ryudocan gene extends approximately 24 kilobases and is divided into five exons, which appear to be conserved in syndecan family members. Exon I encodes the signal peptide; exons II-IV, the extracellular domain; and exon V, the transmembrane and cytoplasmic domains, which are highly homologous among syndecan family members. Primer extension analysis showed that human ryudocan gene had a single transcription initiation site, located 3 bases upstream from the described cDNA [Kojima et al. (1993) BBRC 190, 814-822]. The 5'-flanking sequences of human ryudocan gene contain a TATA-like sequence as well as a variety of other potential binding sites for transcription factors, including Sp1, Ap-2, NF-kB, E-alpha H box, H4TF-2, and LBP-1, and were capable of functioning as a promoter. The determination of the human ryudocan gene structure will allow elucidation of constitutive, cell-specific, tissue-specific, and developmentally regulated expression.