Transcriptional activation of histone H4 by C/EBP? during the mitotic clonal expansion of 3T3-L1 adipocyte differentiation.

ABSTRACT: CCAAT enhancer binding protein ? (C/EBP?) is required for both mitotic clonal expansion (MCE) and terminal differentiation during the 3T3-L1 adipocyte differentiation program. Whereas the mechanism of C/EBP? during terminal differentiation is well understood, the mechanism of C/EBP? in MCE is not. We provide evidence that histone H4, the most conserved cell cycle-related histone, the change of which is strictly correlated with DNA content change during the cell cycle, is transcriptionally activated by C/EBP? during MCE. Expression of histone H4 is increased at 16 h after induction when 3T3-L1 preadipocytes synchronously reenter S phase, which is correlated with the sequential phosphorylation and activation of C/EBP?, and expression was partially suppressed when A-C/EBP (dominant negative for C/EBP protein) was overexpressed. One C/EBP-binding site was identified in one of the histone H4 gene promoters (hist4h4), confirmed by both electrophoretic mobility shift assay and chromatin immunoprecipitation assay. C/EBP-binding sites were also found in 9 of 11 other histone H4 promoters, which can also be transactivated by C/EBP?. Knockdown of C/EBP? by stealth small interfering RNA partially decreased H4 gene expression and arrested cells in G1 phase as indicated by bromodeoxyuridine incorporation and fluorescence-activated cell sorting analysis of DNA content. This study provides new insights into why C/EBP? is required for MCE during 3T3-L1 adipocyte differentiation and why C/EBP? plays important roles in the proliferation of other cell types.

SUBMITTER: Zhang YY 

PROVIDER: S-EPMC3128520 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature