DDB1基因在促进脂肪细胞分化中的作用及机制研究

脂肪细胞功能异常与肥胖病等代谢性疾病的发生密切相关。脂肪细胞分化过程中早期的信号感知和调控目前研究得并不清楚。我们前期研究发现DDB1能够以不依赖于CUL4泛素连接酶的活性促进脂肪细胞的分化，DDB1缺失显著下调脂肪细胞分化早期基因Krox20的表达，提示DDB1以一种新的机制调控脂肪细胞分化的早期转录事件。为了进一步研究DDB1在脂肪细胞分化中的作用和分子机制，我们将：1）利用原代细胞和构建不与CUL4相互作用的DDB1突变体进一步明确DDB1以不依赖于CUL4的方式发挥作用；2）结合RNA-Seq和ChIP-Seq研究DDB1调控ELK1转录激活活性的作用及机制；3）鉴定DDB1的相互作用蛋白，结合ChIP-Seq等技术解析DDB1调控脂肪细胞分化过程中转录起始的分子机制。本研究将揭示DDB1在促进脂肪细胞分化过程中的新机制，丰富脂肪细胞分化早期转录起始的基础理论。

Adipogenesis, the differentiation process from preadipocytes to mature adipocytes, has gained much attention in the past few decades due to its close relevance with the global epidemic in obesity and related metabolic diseases. In response to hormonal signals, a cascade of transcriptional factors is turned on and eventually leads to fully differentiated adipocytes. Although several waves of transcriptional events have been identified, the molecular mechanism of how the transcriptional cascade is initiated remains largely unknown. Our preliminary experiments indicate that Damaged DNA binding protein 1 (DDB1) might play a key role in the process. DDB1 usually functions as a linker of the Cullin4 (CUL4) ubiquitin E3-ligase to interact with a subset of WD40 proteins, which serve as substrate receptors; however, we find that DDB1 works independently of CUL4 to stimulate adipogenesis. In contrast to depletion of CUL4A or CUL4B that promotes adipogenesis, lack of DDB1 in preadipocytes suppresses adipogenesis. And we show that DDB1 is required for the transcription of immediate-early response genes. For further studies, we plan to : 1) Confirm the CUL4-independent function of DDB1 in primary preadipocytes and by generating DDB1 mutant that does not interact with CUL4; 2) Figure out how DDB1 modulates the transcriptional activity of ELK1 using RNA-Seq and ChIP-Seq; 3) Elucidate the mechanism of DDB1 in initiating the transcriptional events in adipogenesis by identifying DDB1-interacting proteins and ChIP-Seq. Our findings will identify a CUL4-independent function of DDB1 in regulating transcriptional initiation in adipogenesis.