title: Forkhead box O1 (FOXO1) protein, but not p53, contributes to robust induction of p21 expression in fasted mice.
abstract: Reporter mice that enable the activity of the endogenous p21 promoter to be dynamically monitored in real time in vivo and under a variety of experimental conditions revealed ubiquitous p21 expression in mouse organs including the brain. Low light bioluminescence microscopy was employed to localize p21 expression to specific regions of the brain. Interestingly, p21 expression was observed in the paraventricular, arcuate, and dorsomedial nuclei of the hypothalamus, regions that detect nutrient levels in the blood stream and signal metabolic actions throughout the body. These results suggested a link between p21 expression and metabolic regulation. We found that short-term food deprivation (fasting) potently induced p21 expression in tissues involved in metabolic regulation including liver, pancreas and hypothalamic nuclei. Conditional reporter mice were generated that enabled hepatocyte-specific expression of p21 to be monitored in vivo. Bioluminescence imaging demonstrated that fasting induced a 7-fold increase in p21 expression in livers of reporter mice and Western blotting demonstrated an increase in protein levels as well. The ability of fasting to induce p21 expression was found to be independent of p53 but dependent on FOXO1. Finally, occupancy of the endogenous p21 promoter by FOXO1 was observed in the livers of fasted but not fed mice. Thus, fasting promotes loading of FOXO1 onto the p21 promoter to induce p21 expression in hepatocytes.
authors.affiliation: From the Department of Cell Biology and Physiology.
authors.forename: Kelsey L
authors.initials: KL
authors.lastname: Tinkum
authors.forename: Lynn S
authors.initials: LS
authors.lastname: White
authors.forename: Luciano
authors.initials: L
authors.lastname: Marpegan
authors.forename: Erik
authors.initials: E
authors.lastname: Herzog
authors.forename: David
authors.initials: D
authors.lastname: Piwnica-Worms
authors.forename: Helen
authors.initials: H
authors.lastname: Piwnica-Worms
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000483:Alleles; D000818:Animals; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D005260:Female; D005508:Food Deprivation; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D005822:Genetic Vectors; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D049449:Luminescence; D008297:Male; D051379:Mice; D011401:Promoter Regions, Genetic; D013312:Stress, Physiological; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D016159:Tumor Suppressor Protein p53
keywords: Bioluminescence; Diet; Foxo; Hypothalamus; Liver; Metabolism; Mouse
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