P300-dependent acetylation of activating transcription factor 5 enhances C/EBP? transactivation of C/EBP? 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 ? (C/EBP?) is an important transcription factor that takes part in both of these processes. C/EBP? not only transactivates C/EBP? and the peroxisome proliferator-activated receptor ? (PPAR?), 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/EBP? will help to explain how C/EBP? 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/EBP? via its direct interaction with C/EBP? (which is mediated via the p300-dependent acetylation of ATF5), leading to enhanced C/EBP? transactivation of C/EBP?. We also show that p300 is important for the interaction of ATF5 with C/EBP? as well as for the binding activity of this complex on the C/EBP? 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/EBP? and examined how C/EBP? and ATF5 (acetylated by a p300-dependent mechanism) regulate the transcription of C/EBP?.

SUBMITTER: Zhao Y 

PROVIDER: S-EPMC3911509 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature