Differential Regulation of Islet-specific Glucose-6-phosphatase Catalytic Subunit-related Protein Gene Transcription by Pax-6 and Pdx-1
Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) is selectively expressed in islet β cells and is a major autoantigen in a mouse model of type I diabetes. The analysis of IGRP-chloramphenicol acetyltransferase (CAT) fusion gene expression through transient transfection...
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Published in | The Journal of biological chemistry Vol. 279; no. 33; pp. 34277 - 34289 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
United States
American Society for Biochemistry and Molecular Biology
13.08.2004
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Subjects | |
Online Access | Get full text |
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Summary: | Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) is selectively expressed in islet β cells and
is a major autoantigen in a mouse model of type I diabetes. The analysis of IGRP-chloramphenicol acetyltransferase (CAT) fusion
gene expression through transient transfection of islet-derived βTC-3 cells revealed that a promoter region, located between
â273 and â254, is essential for high IGRP-CAT fusion gene expression. The sequence of this promoter region does not match
that for any known islet-enriched transcription factor. However, data derived from gel retardation assays, a modified ligation-mediated
polymerase chain reaction in situ footprinting technique and a SDS-polyacrylamide separation/renaturation procedure led to the hypothesis that this protein
might be Pax-6, a conclusion that was confirmed by gel supershift assays. Additional experiments revealed a second non-consensus
Pax-6 binding site in the â306/â274 IGRP promoter region. Pax-6 binding to these elements is unusual in that it appears to
require both its homeo and paired domains. Interestingly, loss of Pax-6 binding to the â273/ â246 element is compensated by
Pax-6 binding to the â306/â274 element and vice versa. Gel retardation assays revealed that another islet-enriched transcription
factor, namely Pdx-1, binds four non-consensus elements in the IGRP promoter. However, mutation of these elements has little
effect on IGRP fusion gene expression. Although chromatin immunoprecipitation assays show that both Pax-6 and Pdx-1 bind to
the IGRP promoter within intact cells, in contrast to the critical role of these factors in β cell-specific insulin gene expression,
IGRP gene transcription appears to require Pax-6 but not Pdx-1. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M404830200 |