Lipogenesis is exquisitely regulated by nutritional/hormonal states. Fatty acid synthase (FAS) is a central enzyme in lipogenesis and is thought to be a rate-limiting step in long-term regulation. FAS transcription is low in the fasted state but increases dramatically with feeding. Increased insulin is largely responsible for the activation of FAS transcription. We showed that feeding/insulin increases SREBP-1c but that, by direct physical interaction, USF bound to the -65 E-box recruits SREBP to bind -150 SRE for activation of the FAS promoter. USF may be a molecular switch during the fasting/feeding and diabetes/insulin transitions. Using tandem affinity purification coupled with mass spectrometry (MS), we recently identified components of the USF holocomplex and found that different components participate in a fasting/feeding dependent manner. By MS analysis, we also detected a feeding- dependent specific site phosphorylation of USF as well as two adjacent sites of USF acetylation.
In Aim 1, once we identify the components of the USF holocomplex, we will examine by chromatin immunoprecipitation differential binding of the various components of USF holocomplex to the FAS promoter in fasting/feeding and diabetes/insulin treatments and correlate binding with the FAS promoter activity and transcription. Transgenic mice carrying CAT gene driven by the various 5'-deletions and mutations of the FAS promoter will allow us to verify the binding sites. We will also characterize direct or indirect interactions of various factors with USF as well as the interacting domains. SiRNA- mediated knockdown experiments will demonstrate the significance of these factors in the regulation of the FAS promoter.
In Aim 2, we will examine specific USF phosphorylation by DNA-dependent protein kinase (DNA-PK) as well as the signaling pathway leading to DNA-PK activation and thus USF phosphorylation. We will also examine specific acetylation/deacetylation of USF via recruitment of P/CAF or HDAC9, which may depend on phosphorylation state of USF. Functional consequences of phosphorylation/acetylation of USF on the regulation of the FAS promoter will be studied. Finally, we will examine posttranslational modifications of USF in vivo by adenovirus mediated gene transfer or by generating transgenic mice. We will also use DNA-PK deficient mice to test the role of DNA-PK for USF function and lipogenesis as well as glucose/insulin homeostasis. Our research will elucidate the USF function as a master regulator of lipogenesis during fasting/feeding and diabetes/insulin transitions and may reveal a novel insulin signaling pathway.

Public Health Relevance

Obesity is a major health problem causing metabolic syndrome and type II diabetes and the control of adiposity is a top priority in managing these diseases. Lipogenesis is critical for lipid accumulation and homeostasis in liver and adipose tissue. This research is to understand metabolic control of lipogenesis and dysregulation in diabetes and obesity and may provide new therapeutic targets.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK081098-02
Application #
7675419
Study Section
Integrative Physiology of Obesity and Diabetes Study Section (IPOD)
Program Officer
Silva, Corinne M
Project Start
2008-08-15
Project End
2012-05-31
Budget Start
2009-06-01
Budget End
2010-05-31
Support Year
2
Fiscal Year
2009
Total Cost
$307,000
Indirect Cost
Name
University of California Berkeley
Department
Nutrition
Type
Schools of Earth Sciences/Natur
DUNS #
124726725
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Viscarra, Jose A; Wang, Yuhui; Hong, Il-Hwa et al. (2017) Transcriptional activation of lipogenesis by insulin requires phosphorylation of MED17 by CK2. Sci Signal 10:
Wang, Yuhui; Viscarra, Jose; Kim, Sun-Joong et al. (2015) Transcriptional regulation of hepatic lipogenesis. Nat Rev Mol Cell Biol 16:678-89
Wang, Yuhui; Wong, Roger H F; Tang, Tianyi et al. (2013) Phosphorylation and recruitment of BAF60c in chromatin remodeling for lipogenesis in response to insulin. Mol Cell 49:283-97
Armengol, Jordi; Villena, Josep A; Hondares, Elayne et al. (2012) Pref-1 in brown adipose tissue: specific involvement in brown adipocyte differentiation and regulatory role of C/EBP?. Biochem J 443:799-810
Wong, Roger H F; Sul, Hei Sook (2010) Insulin signaling in fatty acid and fat synthesis: a transcriptional perspective. Curr Opin Pharmacol 10:684-91
Ahmadian, Maryam; Duncan, Robin E; Sul, Hei Sook (2009) The skinny on fat: lipolysis and fatty acid utilization in adipocytes. Trends Endocrinol Metab 20:424-8
Wong, Roger H F; Sul, Hei Sook (2009) DNA-PK: relaying the insulin signal to USF in lipogenesis. Cell Cycle 8:1977-8
Wong, Roger H F; Chang, Inhwan; Hudak, Carolyn S S et al. (2009) A role of DNA-PK for the metabolic gene regulation in response to insulin. Cell 136:1056-72