Li Duan-Zhuo, Liu Shun-Fang, Zhu Lan, Wang Yu-Xing, Chen Yi-Xiang, Liu Jie, Hu Gang, Yu Xin, Li Jian, Zhang Jin, Wu Zhi-Xiang, Lu Han, Liu Wei, Liu Bin
Hubei Key Laboratory for Kidney Disease Pathogenesis and Intervention, Huangshi Central Hospital of Edong Healthcare Group, Hubei Polytechnic University School of Medicine, Huangshi, Hubei 435003, PR China.
Department of Oncology, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China.
Oncotarget. 2017 Oct 12;8(57):97178-97186. doi: 10.18632/oncotarget.21843. eCollection 2017 Nov 14.
Mof4 family associated protein 1 (MRFAP1) is a 14 kDa nuclear protein, which involves in maintaining normal histone modification levels by negatively regulating recruitment of the NuA4 (nucleosome acetyltransferase of H4) histone acetyltransferase complex to chromatin. MRFAP1 has been identified as one of the most up-regulated proteins after NEDD8 (neural precursor cell expressed developmentally down-regulated 8) inhibition in multiple human cell lines. However, the biological function of MRFAP1 and the E3 ligase that targets MRFAP1 for destruction remain mysterious. Here we show, by using an immunoprecipitation-based proteomics screen, that MRFAP1 is an interactor of the F-box protein FBXW8. MRFAP1 is degraded by means of the ubiquitin ligase Cul7/FBXW8 during mitotic anaphase-telophase transition and accumulated in mitotic metaphase. Overexpression of FBXW8 increased the polyubiquitination and decreased the stability of MRFAP1, whereas knockdown of FBXW8 prolonged the half-life of MRFAP1. Moreover, forced expression of MRFAP1 in HeLa cells caused growth retardation and genomic instability, leading to severe mitotic cell death. Thus, Cul7/FBXW8-mediated destruction of MRFAP1 is a regulatory component monitoring the anaphase-telophase transition and preventing genomic instability.
Mof4家族相关蛋白1（MRFAP1）是一种14 kDa的核蛋白，它通过负向调节NuA4（H4组蛋白乙酰转移酶复合体）组蛋白乙酰转移酶复合体向染色质的募集来维持正常的组蛋白修饰水平。在多种人类细胞系中，MRFAP1已被鉴定为NEDD8（神经前体细胞表达的发育下调蛋白8）抑制后上调最为明显的蛋白之一。然而，MRFAP1的生物学功能以及靶向MRFAP1进行降解的E3连接酶仍然未知。在这里，我们通过基于免疫沉淀的蛋白质组学筛选表明，MRFAP1是F-box蛋白FBXW8的相互作用蛋白。在有丝分裂后期 - 末期转换过程中，MRFAP1通过泛素连接酶Cul7/FBXW8被降解，并在有丝分裂中期积累。FBXW8的过表达增加了MRFAP1的多聚泛素化并降低了其稳定性，而FBXW8的敲低则延长了MRFAP1的半衰期。此外，在HeLa细胞中强制表达MRFAP1会导致生长迟缓以及基因组不稳定，进而导致严重的有丝分裂细胞死亡。因此，Cul7/FBXW8介导的MRFAP1降解是监测后期 - 末期转换并防止基因组不稳定的调控成分。
