| A member of the interferon-inducible p200 family of proteins, p204, has recently been reported to function in the development of many mesoderm-derived tissues, such as bone, muscle, and cartilage. However, no published study has yet investigated the role of p204 in adipogenesis. Our preliminary experiments showed that p204 can be found in 3T3-L1 preadipocytes and its expression was up-regulated in a differentiation-dependent manner. As such, we hypothesized that p204 is associated with adipogenesis and focused on the influence of p204 on adipogenesis.In the present study we investigated the transient elevated expression and cytoplasm-to-nucleus translocation of p204 in the early stage of adipogenesis. To determine the effect of p204 on adipogenesis, p204-siRNA and expression vector were produced for p204 suppression and overexpression, respectively. The knockdown of p204 resulted in a significantly depressed adipocyte differentiation, whereas p204 overexpression promoted adipocyte differentiation. The mRNA expression of adipogenic markers, such as peroxisome-proliferator-activated receptor (PPAR)γ, CCAAT/enhancer-binding-protein (C/EBP)α, lipoprotein lipase (LPL), and adipsin, was decreased by p204 suppression and increased by p204 overexpression. A co-immunoprecipitation assay coupled with an indirect immunofluorescence assay also indicated that p204 interacted and co-localized with C/EBPδin the nucleus. Furthermore, the knockdown of p204 disrupted the interaction between p204 and C/EBPδand partially suppressed the PPARγtranscriptional activity by dissociating C/EBPδwith the PPARγpromoter element.Collectively, our data indicate that the transient expression of p204 in the early stage is indispensable for adipocyte differentiation. Disruption of p204 expression patterns at this stage leads to irreversible damage in fat formation.
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