Deshmukh Dhanraj, Xu Jin, Yang Xi, Shimelis Hermela, Fang Shengyun, Qiu Yun
Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Center for Biomedical Engineering and Technology, Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Pharmaceutics. 2022 Apr 6;14(4):802. doi: 10.3390/pharmaceutics14040802.
The cyclin-dependent kinase inhibitor p27 (Kip1) is an important regulator of the G1/S checkpoint. It is degraded by the SCF-SKP2 complex in late G1 thereby allowing cells to progress to the S phase. Here we investigated the role of the E3 ubiquitin ligase RNF6 (Ring Finger Protein 6) in cell cycle progression in prostate cancer cells. Our data demonstrate that RNF6 can promote cell cycle progression by reducing the levels of p27. Knockdown of RNF6 led to an increase in the stability of p27 and to the arrest of cells in the G1 phase. RNF6 interacted with p27 via its KIL domain and this interaction was found to be phosphorylation independent. RNF6 enhanced ubiquitination and subsequent degradation of p27 in the early G0/G1 phase of the cell cycle. Knockdown of RNF6 expression by short hairpin RNA led to inhibition of the CDK2/Cyclin E complex thereby reducing phosphorylation of Retinoblastoma protein (Rb) and to a subsequent decrease in cell cycle progression and proliferation. Our data suggest that RNF6 acts as a negative regulator for p27 leading to its proteasome-dependent degradation in the early G0/G1 phase of the cell cycle.
细胞周期蛋白依赖性激酶抑制剂p27（Kip1）是G1/S期检查点的重要调节因子。它在G1晚期被SCF-SKP2复合物降解，从而使细胞进入S期。在此，我们研究了E3泛素连接酶RNF6（环指蛋白6）在前列腺癌细胞周期进程中的作用。我们的数据表明，RNF6可通过降低p27水平来促进细胞周期进程。敲低RNF6会导致p27稳定性增加，并使细胞停滞在G1期。RNF6通过其KIL结构域与p27相互作用，且发现这种相互作用不依赖于磷酸化。RNF6在细胞周期的早期G0/G1期增强p27的泛素化及随后的降解。通过短发夹RNA敲低RNF6表达会导致CDK2/细胞周期蛋白E复合物受到抑制，从而减少视网膜母细胞瘤蛋白（Rb）的磷酸化，并随后降低细胞周期进程和增殖。我们的数据表明，RNF6作为p27的负调节因子，导致其在细胞周期早期G0/G1期被蛋白酶体依赖性降解。
