p300-Dependent Acetylation of Activating Transcription Factor 5 Enhances C/EBPβ Transactivation of C/EBPα during 3T3-L1 Differentiation

Abstract

Adipogenesis is a multistep process by which 3T3-L1 preadipocytes differentiate into mature adipocytes through mitotic clonal expansion (MCE) and terminal differentiation. The CCAAT/enhancer-binding protein β (C/EBPβ) is an important transcription factor that takes part in both of these processes. C/EBPβ not only transactivates C/EBPα and the peroxisome proliferator-activated receptor γ (PPARγ), which cause 3T3-L1 preadipocytes to enter terminal adipocyte differentiation, but also is required to activate cell cycle genes necessary for MCE. The identification of potential cofactors of C/EBPβ will help to explain how C/EBPβ undertakes these specialized roles during the different stages of adipogenesis. In this study, we found that activating transcription factor 5 (ATF5) can bind to the promoter of C/EBPα via its direct interaction with C/EBPβ (which is mediated via the p300-dependent acetylation of ATF5), leading to enhanced C/EBPβ transactivation of C/EBPα. We also show that p300 is important for the interaction of ATF5 with C/EBPβ as well as for the binding activity of this complex on the C/EBPα promoter. Consistent with these findings, overexpression of ATF5 and an acetylated ATF5 mimic both promoted 3T3-L1 adipocyte differentiation, whereas short interfering RNA-mediated ATF5 downregulation inhibited this process. Furthermore, we show that the elevated expression of ATF5 is correlated with an obese phenotype in both mice and humans. In summary, we have identified ATF5 as a new cofactor of C/EBPβ and examined how C/EBPβ and ATF5 (acetylated by a p300-dependent mechanism) regulate the transcription of C/EBPα.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00956-13.

ACKNOWLEDGMENTS

We thank Shanghai Jiaotong University Affiliated Ninth People's Hospital for kindly providing patients' subcutaneous adipose tissue.

This work was supported by National Key Basic Research Project grants (2011CB910201 to Q.Q.T. and 2013CB530601 to X.L.), National Natural Science Foundation grants (81270954 and 30870510 to X.L.), the State Key Program of National Natural Science Foundation (31030048 to Q.Q.T.), the Shanghai Rising Star Program (13QH1400800 to X.L.), and the Shanghai New Excellent Medicine Talents Program (XYQ2011037 to X.L.). The Department of Biochemistry and Molecular Biology at Fudan University Shanghai Medical College is supported by the Shanghai Leading Academic Discipline Projects B110 and by 985 Project 985III-YFX0302.