Identification and validation of novel C/EBPbeta-regulated genes in preadipocyte proliferation

CCAAT/enhancer-binding protein beta (C/EBPbeta) is required for mitotic clonal expansion (MCE) during adipogenesis. It is still unclear how C/EBPbeta regulates MCE in the earlier differentiation programs of 3T3-L1 preadipocytes. The purpose of this paper was to understand why C/EBPbeta is required for preadipocyte proliferation, and identify new target genes of C/EBPbeta with chromatin immunoprecipitation (ChIP)-on-chip.

Postconfluent growth-arrested 3T3-L1 preadipocytes were induced to differentiation using a standard differentiation protocol. ChIP was performed at 20 hours after induction with specific anti-C/EBPbeta antibodies. The precipitated DNA was amplified, labeled and hybridized with a mouse promoter microarray. Compared with the control in which the ChIP experiment was performed with non-specific antibody, only the genes with a signal increasing more than 2 fold were considered as candidate genes.

A total of 110 candidate genes were identified. BTG3 associated nuclear protein (SMAR1, Banp) and tripartite motif-containing 35 (Hls5, trim35) were two target genes among the 110 candidate genes which are involved in cell cycle regulation; the binding of C/EBPbeta to the promoter of banp and trim35 was verified by ChIP-PCR.

C/EBPbeta may regulate preadipocyte proliferation through activation of banp and trim35.