Laboratory of Animal Fat Deposition and Muscle Development, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China; Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas, 77030.
J Cell Biochem. 2013 Nov;114(11):2500-12. doi: 10.1002/jcb.24595.
PU.1 is an Ets family transcription factor involved in the myelo-lymphoid differentiation. We have previously demonstrated that PU.1 is also expressed in the adipocyte lineage. However, the expression levels of PU.1 mRNA and protein in preadipocytes do not match the levels in mature adipocytes. PU.1 mRNA level is higher in preadipocytes, whereas its protein is expressed in the adipocytes but not in the preadipocytes. The underlying mechanism remains elusive. Here, we find that miR-155 knockdown or overexpression has no effect on the levels of PU.1 mRNA and protein in preadipocytes or adipocytes. MiR-155 regulates adipogenesis not through PU.1, but via C/EBPβ which is another target of miR-155. We also checked the expression levels of PU.1 mRNA and antisense long non-coding RNA (AS lncRNA). Interestingly, compared with the level of PU.1 mRNA, the level of PU.1 AS lncRNA is much higher in preadipocytes, whereas it is opposite in the adipocytes. We further discover that PU.1 AS lncRNA binds to its mRNA forming an mRNA/AS lncRNA compound. The knockdown of PU.1 AS by siRNA inhibits adipogenesis and promotes PU.1 protein expression in both preadipocytes and adipocytes. Furthermore, the repression of PU.1 AS decreases the expression and secretion of adiponectin. We also find that the effect of retroviral-mediated PU.1 AS knockdown on adipogenesis is consistent with that of PU.1 AS knockdown by siRNA. Taken together, our results suggest that PU.1 AS lncRNA promotes adipogenesis through preventing PU.1 mRNA translation via binding to PU.1 mRNA to form mRNA/AS lncRNA duplex in preadipocytes.
PU.1 是一种 Ets 家族转录因子，参与骨髓 - 淋巴分化。我们之前已经证明，PU.1 也在脂肪细胞谱系中表达。然而，前脂肪细胞中 PU.1 的 mRNA 和蛋白表达水平与成熟脂肪细胞不匹配。前脂肪细胞中 PU.1 mRNA 水平较高，而其蛋白则在脂肪细胞中表达，而在前脂肪细胞中不表达。潜在的机制仍不清楚。在这里，我们发现 miR-155 的敲低或过表达对前脂肪细胞或脂肪细胞中 PU.1 mRNA 和蛋白的水平没有影响。miR-155 不是通过 PU.1 调节脂肪生成，而是通过 C/EBPβ，C/EBPβ是 miR-155 的另一个靶标。我们还检查了 PU.1 mRNA 和反义长非编码 RNA（AS lncRNA）的表达水平。有趣的是，与 PU.1 mRNA 的水平相比，前脂肪细胞中 PU.1 AS lncRNA 的水平要高得多，而在脂肪细胞中则相反。我们进一步发现，PU.1 AS lncRNA 与其 mRNA 结合形成 mRNA/AS lncRNA 复合物。siRNA 敲低 PU.1 AS 抑制前脂肪细胞和脂肪细胞中的脂肪生成，并促进 PU.1 蛋白表达。此外，PU.1 AS 的抑制降低了脂联素的表达和分泌。我们还发现，逆转录病毒介导的 PU.1 AS 敲低对脂肪生成的影响与 siRNA 敲低 PU.1 AS 的影响一致。总之，我们的结果表明，PU.1 AS lncRNA 通过与 PU.1 mRNA 结合形成 mRNA/AS lncRNA 双链体来阻止 PU.1 mRNA 的翻译，从而促进前脂肪细胞中的脂肪生成。
