XIHbox 8, an endoderm-specific Xenopus homeodomain protein, is closely related to a mammalian insulin gene transcription factor.
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.
Peshavaria
M
M
Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232.
Gamer
L
L
Henderson
E
E
Teitelman
G
G
Wright
C V
CV
Stein
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002467:Cell Nucleus / Q000737:chemistry / Q000648:ultrastructure; D006224:Cricetinae; D004247:DNA / Q000032:analysis / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics*; D007150:Immunohistochemistry; D007328:Insulin / Q000235:genetics*; D007340:Insulinoma / Q000737:chemistry / Q000473:pathology / Q000648:ultrastructure; D007515:Islets of Langerhans / Q000737:chemistry / Q000166:cytology / Q000648:ultrastructure; D051379:Mice; D008969:Molecular Sequence Data; D010190:Pancreatic Neoplasms / Q000737:chemistry / Q000473:pathology / Q000648:ultrastructure; D051381:Rats; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013004:Somatostatin / Q000032:analysis / Q000235:genetics; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics*; D014407:Tumor Cells, Cultured; D014981:Xenopus / Q000235:genetics*; D029867:Xenopus Proteins
D018398:Homeodomain Proteins; D007328:Insulin; C089627:PDX1 protein, Xenopus; D014157:Transcription Factors; D029867:Xenopus Proteins; D013004:Somatostatin; D004247:DNA