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Biochem Biophys Res Commun. 2014 Jul 25;450(2):979-83. doi: 10.1016/j.bbrc.2014.06.080. Epub 2014 Jun 24.

Identification of functional glucocorticoid response elements in the mouse FoxO1 promoter.

Author information

1
Center of Excellence for the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, Bronx, NY, United States; Department of Medicine, Mount Sinai School of Medicine, New York, NY, United States. Electronic address: weiping.qin@mssm.edu.
2
Center of Excellence for the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, Bronx, NY, United States.
3
Center of Excellence for the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, Bronx, NY, United States; Department of Medicine, Mount Sinai School of Medicine, New York, NY, United States; Rehabilitation Medicine, Mount Sinai School of Medicine, New York, NY, United States.

Abstract

Glucocorticoids stimulate muscle atrophy through a cascade of signals that includes activation of FoxO transcription factors which then upregulate multiple genes to promote degradation of myofibrillar and other muscle proteins and inhibit protein synthesis. Our previous finding that glucocorticoids upregulate mRNA levels for FoxO1 in skeletal muscle led us to hypothesize that the FoxO1 gene contains one or more glucocorticoid response elements (GREs). Here we show that upregulation of FoxO1 expression by glucocorticoids requires the glucocorticoid receptor (GR) and binding of hormones to it. In cultured C2C12 myoblasts dexamethasone did not alter FoxO1 mRNA stability. Computational analysis predicted that the proximal promoter of the FoxO1 gene contained a cluster of eight GRE half sites and one highly conserved near-consensus SRE; the cluster is found between -800 and -2000bp upstream of the first codon of the FoxO1 gene. A reporter gene constructed using the first 2kb of the FoxO1 promoter was stimulated by dexamethasone. Removal of a 5' domain containing half of the GREs reduced reporter gene activity and removal of all GREs in this region ablated activation by dexamethasone. Restriction fragments of the cluster of 8 upstream GREs bound recombinant GR in gel shift assays. Collectively, the data demonstrate that the proximal promoter of the FoxO1 gene contains multiple functional GREs, indicating that upregulation of FoxO1 expression by glucocorticoids through GREs represents an additional mechanism by which the GR drives glucocorticoid-mediated muscle atrophy. These findings are also relevant to other physiological roles of FoxO1 such as regulation of hepatic metabolism.

KEYWORDS:

FoxO1; Glucocorticoid receptor; Glucocorticoid response element; Glucocorticoids

PMID:
24971545
DOI:
10.1016/j.bbrc.2014.06.080
[Indexed for MEDLINE]

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