van Beekum Olivier, Brenkman Arjan B, Grøntved Lars, Hamers Nicole, van den Broek Niels J F, Berger Ruud, Mandrup Susanne, Kalkhoven Eric
Department of Metabolic and Endocrine Diseases, University Medical Center Utrecht, Lundlaan 6, Utrecht, The Netherlands.
Endocrinology. 2008 Apr;149(4):1840-9. doi: 10.1210/en.2007-0977. Epub 2007 Dec 20.
The transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) plays a key role in the regulation of lipid and glucose metabolism in adipocytes, by regulating their differentiation, maintenance, and function. The transcriptional activity of PPARgamma is dictated by the set of proteins with which this nuclear receptor interacts under specific conditions. Here we identify the HIV-1 Tat-interacting protein 60 (Tip60) as a novel positive regulator of PPARgamma transcriptional activity. Using tandem mass spectrometry, we found that PPARgamma and the acetyltransferase Tip60 interact in cells, and through use of chimeric proteins, we established that coactivation by Tip60 critically depends on the N-terminal activation function 1 of PPARgamma, a domain involved in isotype-specific gene expression and adipogenesis. Chromatin immunoprecipitation experiments showed that the endogenous Tip60 protein is recruited to PPARgamma target genes in mature 3T3-L1 adipocytes but not in preadipocytes, indicating that Tip60 requires PPARgamma for its recruitment to PPARgamma target genes. Importantly, we show that in common with disruption of PPARgamma function, small interfering RNA-mediated reduction of Tip60 protein impairs differentiation of 3T3-L1 preadipocytes. Taken together, these findings qualify the acetyltransferase Tip60 as a novel adipogenic factor.
转录因子过氧化物酶体增殖物激活受体γ（PPARγ）通过调节脂肪细胞的分化、维持和功能，在脂质和葡萄糖代谢调控中发挥关键作用。PPARγ的转录活性取决于该核受体在特定条件下与之相互作用的一组蛋白质。在此，我们鉴定出HIV-1 Tat相互作用蛋白60（Tip60）是PPARγ转录活性的一种新型正向调节因子。通过串联质谱分析，我们发现PPARγ与乙酰转移酶Tip60在细胞中相互作用，并且通过使用嵌合蛋白，我们确定Tip60的共激活关键取决于PPARγ的N端激活功能1，该结构域参与同型特异性基因表达和脂肪生成。染色质免疫沉淀实验表明，内源性Tip60蛋白在成熟的3T3-L1脂肪细胞中被募集到PPARγ靶基因，但在前脂肪细胞中则不然，这表明Tip60需要PPARγ才能被募集到PPARγ靶基因。重要的是，我们表明，与PPARγ功能破坏一样，小干扰RNA介导的Tip60蛋白减少会损害3T3-L1前脂肪细胞的分化。综上所述，这些发现使乙酰转移酶Tip60成为一种新型脂肪生成因子。
