CCNE1和E2F1部分抑制剪接抑制素 A 治疗引起的 G1 期阻滞

CCNE1 and E2F1 Partially Suppress G1 Phase Arrest Caused by Spliceostatin A Treatment

The potent splicing inhibitor spliceostatin A (SSA) inhibits cell cycle progression at the G1 and G2/M phases. We previously reported that upregulation of the p27 cyclin-dependent kinase inhibitor encoded by CDKN1B and its C-terminal truncated form, namely p27*, which is translated from CDKN1B pre-mRNA, is one of the causes of G1 phase arrest caused by SSA treatment. However, the detailed molecular mechanism underlying G1 phase arrest caused by SSA treatment remains to be elucidated. In this study, we found that SSA treatment caused the downregulation of cell cycle regulators, including CCNE1, CCNE2, and E2F1, at both the mRNA and protein levels. We also found that transcription elongation of the genes was deficient in SSA-treated cells. The overexpression of CCNE1 and E2F1 in combination with CDKN1B knockout partially suppressed G1 phase arrest caused by SSA treatment. These results suggest that the downregulation of CCNE1 and E2F1 contribute to the G1 phase arrest induced by SSA treatment, although they do not exclude the involvement of other factors in SSA-induced G1 phase arrest.

有效的剪接抑制剂 spliceostatin A (SSA) 抑制 G1 和 G2/M 期的细胞周期进程。我们之前报道过由CDKN1B编码的 p27 细胞周期蛋白依赖性激酶抑制剂及其 C 端截短形式，即从CDKN1B前体 mRNA翻译而来的 p27* 的上调是 SSA 治疗引起的 G1 期停滞的原因之一. 然而，由 SSA 治疗引起的 G1 期停滞的详细分子机制仍有待阐明。在这项研究中，我们发现，SSA治疗导致细胞周期调控的下调，包括CCNE1，CCNE2和E2F1, 在 mRNA 和蛋白质水平。我们还发现 SSA 处理的细胞中基因的转录延长是有缺陷的。的过表达CCNE1和E2F1与组合CDKN1B敲除部分抑制引起的SSA治疗G1期阻滞。这些结果表明CCNE1和E2F1的下调有助于 SSA 治疗诱导的 G1 期停滞，尽管它们不排除其他因素参与 SSA 诱导的 G1 期停滞。

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Cell cycle progression is closely controlled by cell cycle regulators. Among these reg‐ulators, cyclin family proteins and cyclin‐dependent kinases (CDKs) promote cell cycleprogression [1,2]. In G1/S phase transition, cyclin E1 and cyclin E2 (collectively known ascyclin E), along with Cdk2, are the key players that phosphorylate a variety of substrates[3–6]. Rb is a substrate of the cyclin E–Cdk2 complex; it binds the E2F1 transcription factorand represses the transcriptional activity of E2F1 [7,8]. After phosphorylation by cyclin E–Cdk2, Rb releases E2F1, and E2F1, in turn, activates the transcription of numerous genesthat drive the initiation of the S phase. The genes encoding cyclin E are controlled by E2F1,and thus the cyclin E–Cdk2 complex and E2F1 form a positive feedback loop that pro‐motes G1/S phase transition [3,4,6,9]. The cyclin E–Cdk2 complex also phosphorylatesSmad3, CBP/p300, and NPAT, leading to cell cycle progression [10–13]. Conversely, CDKinhibitors repress cell cycle progression by inhibiting the kinase activity of CDKs [2,9].p27 is one of the CDK inhibitors that control G1/S phase transition [9,14,15]. It binds toand inhibits the cyclin E–Cdk2 complex to block cell cycle progression at the G1 phase.The cyclin E–Cdk2 complex negatively regulates p27 through phosphorylation of p27,which induces ubiquitination and proteasomal degradation of p27 [16–18]. Collectively,these factors regulate G1/S phase transition in a coordinated manner.、

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细胞周期的进展受到细胞周期调节因子的密切控制。其中注册检测细胞周期蛋白家族蛋白和细胞周期蛋白依赖激酶(CDKs)促进细胞周期进展[1,2]。在G1/S相变中，cyclin E1和cyclin E2(统称为cyclin E)和Cdk2是磷酸化多种底物的关键分子(3 - 6)。Rb是cyclin E-Cdk2复合物的底物;它与E2F1转录因子结合并抑制E2F1的转录活性[7,8]。经cyclin E -磷酸化后Cdk2、Rb释放E2F1，而E2F1反过来激活许多基因的转录驱动S阶段的开始。编码周期素E的基因由E2F1控制，因此，cyclin E-Cdk2复合物和E2F1形成了一个正反馈回路motes G1/S相变[3,4,6,9]。周期蛋白E-Cdk2复合物也磷酸化Smad3、CBP/p300和NPAT导致细胞周期进展[10-13]。相反,CDK抑制剂通过抑制CDKs的激酶活性来抑制细胞周期进程[2,9]。p27是控制G1/S相变的CDK抑制剂之一[9,14,15]。并抑制cyclin E-Cdk2复合物在G1期阻断细胞周期进程。cyclin E-Cdk2复合物通过p27的磷酸化负调控p27，诱导p27的泛素化和蛋白酶体降解[16-18]。总的来说,这些因素协同调节G1/S相变。

来源：MDPI https://www.mdpi.com/1422-0067/22/21/11623