The repression of IRS2 gene by ATF3, a stress-inducible gene, contributes to pancreatic beta-cell apoptosis.
OBJECTIVE
beta-Cell failure is an essential component of all types of diabetes, and the insulin receptor substrate 2 (IRS2) branch of signaling plays a key role in beta-cell survival and function. We tested the hypothesis that activating transcription factor 3 (ATF3), a stress-inducible proapoptotic gene, downregulates the expression of IRS2 in beta-cells.


METHODS
We used both the gain- and loss-of-function approaches to test the effects of ATF3 on IRS2 gene expression. We also analyzed the binding of ATF3 to the IRS2 promoter by chromatin immunoprecipitation assay and the transcription of the IRS2 gene by polymerase II occupancy assay. Furthermore, we tested the ability of IRS2 to alleviate the proapoptotic effects of ATF3 in cultured beta-cells and in transgenic mice using the rat insulin promoter to drive the transgenes.


RESULTS
Expression of ATF3 is sufficient to reduce IRS2 gene expression; in contrast, knockdown or knockout of ATF3 reduces the ability of stress signals to downregulate IRS2 expression. ATF3 binds to the IRS2 promoter in vivo, and the binding of ATF3 correlates with decreased IRS2 gene transcription. Functionally, expression of IRS2 protects beta-cells from ATF3-induced apoptosis.


CONCLUSIONS
IRS2 is a target gene of ATF3, and its repression by ATF3 contributes, at least partly, to the apoptosis induced by ATF3. Because ATF3 is a stress-inducible gene, our work provides a direct link to explain how environmental stress factors can modulate IRS2 gene transcription.
Li
Dan
D
Department of Molecular and Cellular Biochemistry, Center for Molecular Neurobiology, Ohio State University, Columbus, OH 43210, USA.
Yin
Xin
X
Zmuda
Erik J
EJ
Wolford
Christopher C
CC
Dong
Xiaocheng
X
White
Morris F
MF
Hai
Tsonwin
T
D051700:Activating Transcription Factor 3 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D002478:Cells, Cultured; D015536:Down-Regulation; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D051381:Rats; D013312:Stress, Physiological; D013997:Time Factors
D051700:Activating Transcription Factor 3; C103002:Atf3 protein, mouse; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526298:Irs2 protein, mouse; C526299:Irs2 protein, rat; D010750:Phosphoproteins