Interferon gamma-dependent induction of human intercellular adhesion molecule-1 gene expression involves activation of a distinct STAT protein complex.
In response to interferon gamma (IFNgamma), intercellular adhesion molecule-1 (ICAM-1) is expressed on human keratinocytes, a cell type that is critically involved in cutaneous inflammation. An ICAM-1 5' regulatory region palindromic response element, pIgammaRE, has been shown to confer IFNgamma-dependent transcription enhancement. By electrophoretic mobility shift assays (EMSA), pIgammaRE forms a distinct complex with proteins from IFNgamma-treated human keratinocytes, termed gamma response factor (GRF). Binding of GRF is tyrosine phosphorylation-dependent, and mutations of pIgammaRE that disrupt the palindromic sequence or alter its spatial relationship abrogate GRF binding. Supershift EMSAs using antibodies to characterized STAT proteins suggest that GRF contains a Stat1alpha-like protein; however, non-ICAM-1 IFNgamma-responsive elements (REs) known to bind Stat1alpha homodimers fail to compete for GRF binding in EMSA, and pIgammaRE does not cross-compete with these REs that complex with homodimeric stat1alpha. The pIgammaRE x GRF complex also displays a distinctly different electrophoretic mobility compared to that of IFNgammaREs complexed to homodimeric Stat1alpha. These findings indicate that a distinct complex containing a Stat1alpha-like protein mediates IFNgamma-induced ICAM-1 gene transcription and identifies a subset of IFNgamma-responsive genes that appear to be regulated by this complex.
Naik
S M
SM
Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Shibagaki
N
N
Li
L J
LJ
Quinlan
K L
KL
Paxton
L L
LL
Caughman
S W
SW
D004268:DNA-Binding Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics*; D007371:Interferon-gamma / Q000494:pharmacology*; D015603:Keratinocytes / Q000378:metabolism; D010766:Phosphorylation; D050794:STAT1 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D004268:DNA-Binding Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators; D018799:Intercellular Adhesion Molecule-1; D014443:Tyrosine; D007371:Interferon-gamma