Transcriptional regulation of the human polymeric immunoglobulin receptor gene by interferon-gamma.
IgA is transported into external secretions by the polymeric Ig receptor (pIgR). Interferon-gamma (IFN-gamma), a major regulator of pIgR expression, has been shown to increase pIgR mRNA levels in HT-29 human colon carcinoma cells. To determine the molecular mechanisms of pIgR regulation, genomic DNA containing the 5'-flanking region of the human pIgR gene was isolated and a single start site of transcription in human intestinal epithelial cells was identified. Using chimeric reporter plasmids containing flanking regions of the pIgR gene, a segment of the pIgR promoter which is necessary and sufficient for induction of transcription by IFN-gamma in HT-29 cells was identified. Significantly, the pIgR promoter contains three motifs homologous to the interferon-stimulated response element (ISRE), two in the 5'-flanking region and one in exon 1 of the pIgR gene. The upstream ISREs bind nuclear protein(s) which are constitutively expressed by HT-29 cells, while the exon 1 ISRE binds interferon regulatory factor-1 (IRF-1), following stimulation with IFN-gamma. Furthermore, induction of the IRF-1 promoter by IFN-gamma correlates with induction of the pIgR promoter by IFN-gamma. It has previously been demonstrated that induction of pIgR mRNA by IFN-gamma, requires de novo protein synthesis. It is now shown that IRF-1 is not detected in nuclear extracts from HT-29 cells stimulated with IFN-gamma in the presence of cycloheximide, suggesting that de novo synthesis of IRF-1 is required for induction of pIgR transcription by IFN-gamma.
Piskurich
J F
JF
Institute of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.
Youngman
K R
KR
Phillips
K M
KM
Hempen
P M
PM
Blanchard
M H
MH
France
J A
JA
Kaetzel
C S
CS
D001483:Base Sequence; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005091:Exons / Q000276:immunology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D019073:HT29 Cells; D006801:Humans; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000276:immunology; D019056:Receptors, Polymeric Immunoglobulin / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects / Q000276:immunology*
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D009687:Nuclear Proteins; D010750:Phosphoproteins; D019056:Receptors, Polymeric Immunoglobulin; D007371:Interferon-gamma; D003513:Cycloheximide