Identification of the human alpha6 integrin gene promoter

DNA Cell Biol. 1997 Aug;16(8):929-37. doi: 10.1089/dna.1997.16.929.


The alpha6 integrin subunit couples with either the beta1 or the beta4 subunit to form a laminin receptor. alpha6 expression is cell-type-specific and generally is present at high levels in epithelial and endothelial cells. To study its gene regulation, we isolated a genomic clone containing the human alpha6 integrin gene promoter. It includes 3 kb of the upstream flanking region, the first exon (385 bp), and 9 kb of the first intron. The alpha6 promoter directs transcription initiation from a primary site 202 nucleotides from the translation initiation codon. Unlike most other integrin gene promoters, the alpha6 promoter has a TATA box (GATAAA), which is located 22 nucleotides upstream from the primary transcription initiation site. A 190-bp region upstream from the TATA box is highly rich (78%) in C and G nucleotides and contains several Sp1 and AP2 binding sequences. However, full promoter activity (in the presence of the SV40 enhancer) requires only 78 bp of this C/G-rich sequence upstream from the TATA box. Slightly upstream from the C/G-rich region are a steroid receptor binding homolog and an epithelial-cell-specific E-pal sequence. Another possible epithelial cell-specific binding sequence (Ker1) is found immediately downstream from the TATA box. Cell-type-specific activities of the promoter paralleled the alpha6 mRNA levels in four tested cell lines. In the presence of the SV40 enhancer, alpha6 promoter activity increased approximately four-fold in primary keratinocytes and in HT1080 fibrosarcoma cells and 30-fold in T47D breast carcinoma cells, but remained undetectable in K562 leukemia cells. Genomic analysis that compared alpha6-expressing with non-alpha6-expressing cells suggested that DNA methylation is not involved in the silencing of the alpha6 gene in alpha6-negative cells. DNase I footprint analysis confirmed the binding of Sp1 and AP2 to their cognate sequences. A nuclear extract of high-alpha6-expressing HBL-100 cells also produced significant binding to these sites, suggesting that the two transcription factors are probably involved in the positive regulation of the alpha6 promoter.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Antigens, CD / biosynthesis*
  • Antigens, CD / genetics*
  • Base Sequence
  • Binding Sites
  • Cell Line
  • Cells, Cultured
  • DNA-Binding Proteins / metabolism
  • Humans
  • Infant, Newborn
  • Integrin alpha6
  • Keratinocytes / cytology
  • Keratinocytes / metabolism
  • Kinetics
  • Male
  • Molecular Sequence Data
  • Promoter Regions, Genetic*
  • Recombinant Fusion Proteins / biosynthesis
  • Skin / cytology
  • Skin / metabolism
  • TATA Box
  • Transcription, Genetic
  • Transfection
  • Tumor Cells, Cultured


  • Antigens, CD
  • DNA-Binding Proteins
  • Integrin alpha6
  • Recombinant Fusion Proteins