College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, China; School of Physical Education, Yan'an University, Yan'an, Shaanxi, China.
College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, China.
Arch Biochem Biophys. 2019 Aug 15;671:235-244. doi: 10.1016/j.abb.2019.05.005. Epub 2019 May 7.
Transforming growth factor β (TGFβ) has participated in a variety of cellular biological processes. Smad2 and Smad3 are equally important TGFβ downstream effectors in mediating TGFβ signals. However, genes involved in controlling the balance between these two signaling pathways are unknown. In this study, we showed that although Smad2 and Smad3 are structurally similar, with 89% amino acid sequence similarity in bovine, Smad3 significantly decreased Smad2 mRNA and protein expression during bovine myoblast differentiation, but not by binding on its promoter. Luciferase assays and electrophoretic mobility shift assays (EMSA) demonstrated that the transcription factors C/EBPα and C/EBPβ activate Smad2 promoter activity and expression under high serum medium (GM), whereas the opposite was observed under low serum medium (DM). Moreover, over-expression and interference assays revealed that Smad3 has a different effect on C/EBPα and C/EBPβ expression under GM versus DM conditions. After mutation of the C/EBPα and C/EBPβ binding sites, Smad3 had a reduced effect on Smad2 promoter activity. Therefore, these results demonstrated that Smad3 inhibits Smad2 expression via its transcription factors C/EBPα and C/EBPβ during bovine myoblast differentiation. This novel mechanism of the Smad2/3 genes may offer clues for further investigation of TGFβ signal function.
转化生长因子β（TGFβ）参与了多种细胞生物学过程。Smad2 和 Smad3 是介导 TGFβ信号的同等重要的 TGFβ下游效应物。然而，控制这两种信号通路之间平衡的基因尚不清楚。在本研究中，我们表明，尽管 Smad2 和 Smad3 在结构上相似，在牛中具有 89%的氨基酸序列相似性，但 Smad3 在牛肌母细胞分化过程中显著降低了 Smad2 mRNA 和蛋白表达，而不是通过结合其启动子。荧光素酶测定和电泳迁移率变动分析（EMSA）表明，转录因子 C/EBPα 和 C/EBPβ 在高血清培养基（GM）中激活 Smad2 启动子活性和表达，而在低血清培养基（DM）中则相反。此外，过表达和干扰实验表明，Smad3 在 GM 与 DM 条件下对 C/EBPα 和 C/EBPβ 表达具有不同的影响。在 C/EBPα 和 C/EBPβ 结合位点突变后，Smad3 对 Smad2 启动子活性的影响降低。因此，这些结果表明，Smad3 通过其转录因子 C/EBPα 和 C/EBPβ 在牛肌母细胞分化过程中抑制 Smad2 表达。Smad2/3 基因的这种新机制可能为进一步研究 TGFβ 信号功能提供线索。
