XIHbox 8, an endoderm-specific Xenopus homeodomain protein, is closely related to a mammalian insulin gene transcription factor

Mol Endocrinol. 1994 Jun;8(6):806-16. doi: 10.1210/mend.8.6.7935494.


The cis-acting sequences that mediate insulin gene expression exclusively in pancreatic islet beta-cells are localized within the 5'-flanking region between nucleotides -340 and -91. We have identified an evolutionarily conserved, A+T-rich element at -201/-196 basepairs in the rat insulin II gene that is essential for efficient expression in beta-cells. Affinity-purified antibody to the XIHbox 8 protein super-shifted the major beta-cell-activator factor complex binding to the -201/-196 element. XIHbox 8 is a Xenopus endoderm-specific homeodomain protein whose expression is restricted to the nucleus of endodermal cells of the duodenum and developing pancreas. Antibody to XIHbox 8 specifically interacts with a 47-kilodalton protein present in this DNA complex. Immunohistochemical studies revealed XIHbox 8-like proteins within the nucleus of almost all mouse islet beta-cells and a subset of islet alpha- and beta-cells. These results are consistent with the proposal that an XIHbox 8-related homeoprotein of 47 kilodalton is required for expression of the mammalian insulin gene in beta-cells. Experiments conducted with antiserum raised to somatostatin transcription factor-1 (STF-1), a recently isolated mammalian XIHbox 8-related homeoprotein, indicate that the STF-1 protein is the mammalian homolog of Xenopus XIHbox 8.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Blotting, Western
  • Cell Nucleus / chemistry
  • Cell Nucleus / ultrastructure
  • Cricetinae
  • DNA / analysis
  • DNA / genetics
  • Electrophoresis, Polyacrylamide Gel
  • Genes, Homeobox
  • Homeodomain Proteins / genetics*
  • Immunohistochemistry
  • Insulin / genetics*
  • Insulinoma / chemistry
  • Insulinoma / pathology
  • Insulinoma / ultrastructure
  • Islets of Langerhans / chemistry
  • Islets of Langerhans / cytology
  • Islets of Langerhans / ultrastructure
  • Mice
  • Molecular Sequence Data
  • Pancreatic Neoplasms / chemistry
  • Pancreatic Neoplasms / pathology
  • Pancreatic Neoplasms / ultrastructure
  • Rats
  • Sequence Homology, Amino Acid
  • Sequence Homology, Nucleic Acid
  • Somatostatin / analysis
  • Somatostatin / genetics
  • Transcription Factors / analysis
  • Transcription Factors / genetics*
  • Tumor Cells, Cultured
  • Xenopus / genetics*
  • Xenopus Proteins*


  • Homeodomain Proteins
  • Insulin
  • PDX1 protein, Xenopus
  • Transcription Factors
  • Xenopus Proteins
  • Somatostatin
  • DNA