Kim A-Reum, Sung Jee Young, Rho Seung Bae, Kim Yong-Nyun, Yoon Kyungsil
Division of Translational Science, Research Institute, National Cancer Center, Goyang 10408, Republic of Korea.
Division of Clinical Research, Research Institute, National Cancer Center, Goyang 10408, Republic of Korea.
Biomol Ther (Seoul). 2019 Mar 1;27(2):231-239. doi: 10.4062/biomolther.2019.021.
Suppressor of Variegation 3-9 Homolog 2 (SUV39H2) methylates the lysine 9 residue of histone H3 and induces heterochromatin formation, resulting in transcriptional repression or silencing of target genes. SUV39H1 and SUV39H2 have a role in embryonic development, and SUV39H1 was shown to suppress cell cycle progression associated with Rb. However, the function of human SUV39H2 has not been extensively studied. We observed that forced expression of SUV39H2 decreased cell proliferation by inducing G1 cell cycle arrest. In addition, SUV39H2 was degraded through the ubiquitin-proteasomal pathway. Using yeast two-hybrid screening to address the degradation mechanism and function of SUV39H2, we identified translationally controlled tumor protein (TCTP) as an SUV39H2-interacting molecule. Mapping of the interacting regions indicated that the N-terminal 60 amino acids (aa) of full-length SUV39H2 and the C-terminus of TCTP (120-172 aa) were critical for binding. The interaction of SUV39H2 and TCTP was further confirmed by co-immunoprecipitation and immunofluorescence staining for colocalization. Moreover, depletion of TCTP by RNAi led to up-regulation of SUV39H2 protein, while TCTP overexpression reduced SUV39H2 protein level. The half-life of SUV39H2 protein was significantly extended upon TCTP depletion. These results clearly indicate that TCTP negatively regulates the expression of SUV39H2 post-translationally. Furthermore, SUV39H2 induced apoptotic cell death in TCTP-knockdown cells. Taken together, we identified SUV39H2, as a novel target protein of TCTP and demonstrated that SUV39H2 regulates cell proliferation of lung cancer cells.
异染色质蛋白3-9同源物2（SUV39H2）使组蛋白H3的赖氨酸9残基甲基化并诱导异染色质形成，导致靶基因的转录抑制或沉默。SUV39H1和SUV39H2在胚胎发育中起作用，并且已表明SUV39H1抑制与Rb相关的细胞周期进程。然而，人类SUV39H2的功能尚未得到广泛研究。我们观察到，SUV39H2的强制表达通过诱导G1期细胞周期停滞而降低细胞增殖。此外，SUV39H2通过泛素-蛋白酶体途径降解。利用酵母双杂交筛选来研究SUV39H2的降解机制和功能，我们鉴定出翻译控制肿瘤蛋白（TCTP）是一种与SUV39H2相互作用的分子。相互作用区域的定位表明，全长SUV39H2的N端60个氨基酸（aa）和TCTP的C端（120-172 aa）对于结合至关重要。通过共免疫沉淀和免疫荧光染色共定位进一步证实了SUV39H2与TCTP的相互作用。此外，RNAi介导的TCTP缺失导致SUV39H2蛋白上调，而TCTP过表达降低了SUV39H2蛋白水平。TCTP缺失后，SUV39H2蛋白的半衰期显著延长。这些结果清楚地表明，TCTP在翻译后对SUV39H2的表达起负调控作用。此外，SUV39H2在TCTP敲低的细胞中诱导凋亡性细胞死亡。综上所述，我们鉴定出SUV39H2是TCTP的一种新型靶蛋白，并证明SUV39H2调节肺癌细胞的增殖。
