Transcriptional regulation of FoxO3 gene by glucocorticoids in murine myotubes

Author:

Kuo Taiyi12,Liu Patty H.2,Chen Tzu-Chieh2,Lee Rebecca A.12,New Jenny2,Zhang Danyun2,Lei Cassandra2,Chau Andy2,Tang Yicheng2,Cheung Edna2,Wang Jen-Chywan12ORCID

Affiliation:

1. Endocrinology Graduate Program, University of California Berkeley, Berkeley, California; and

2. Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California

Abstract

Glucocorticoids and FoxO3 exert similar metabolic effects in skeletal muscle. FoxO3 gene expression was increased by dexamethasone (Dex), a synthetic glucocorticoid, both in vitro and in vivo. In C2C12 myotubes the increased expression is due to, at least in part, the elevated rate of FoxO3 gene transcription. In the mouse FoxO3 gene, we identified three glucocorticoid receptor (GR) binding regions (GBRs): one being upstream of the transcription start site, −17kbGBR; and two in introns, +45kbGBR and +71kbGBR. Together, these three GBRs contain four 15-bp glucocorticoid response elements (GREs). Micrococcal nuclease (MNase) assay revealed that Dex treatment increased the sensitivity to MNase in the GRE of +45kbGBR and +71kbGBR upon 30- and 60-min Dex treatment, respectively. Conversely, Dex treatment did not affect the chromatin structure near the −17kbGBR, in which the GRE is located in the linker region. Dex treatment also increased histone H3 and/or H4 acetylation in genomic regions near all three GBRs. Moreover, using chromatin conformation capture (3C) assay, we showed that Dex treatment increased the interaction between the −17kbGBR and two genomic regions: one located around +500 bp and the other around +73 kb. Finally, the transcriptional coregulator p300 was recruited to all three GBRs upon Dex treatment. The reduction of p300 expression decreased FoxO3 gene expression and Dex-stimulated interaction between distinct genomic regions of FoxO3 gene identified by 3C. Overall, our results demonstrate that glucocorticoids activated FoxO3 gene transcription through multiple GREs by chromatin structural change and DNA looping.

Funder

HHS | NIH | National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Muscular Dystrophy Association (MDA)

Tobacco-Related Disease Research Program (TRDRP)

Publisher

American Physiological Society

Subject

Physiology (medical),Physiology,Endocrinology, Diabetes and Metabolism

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