Zhao L, Zhang Y, Gao Y, Geng P, Lu Y, Liu X, Yao R, Hou P, Liu D, Lu J, Huang B
The Key Laboratory of Molecular Epigenetics of Ministry of Education, Northeast Normal University, Changchun, China.
The Institute of Genetics and Cytology, Northeast Normal University, Changchun, China.
Cell Death Differ. 2015 Oct;22(10):1630-40. doi: 10.1038/cdd.2015.6. Epub 2015 Feb 20.
Primary human fibroblasts undergoing oncogene-induced or replicative senescence are known to form senescence-associated heterochromatin foci (SAHF), which can stabilize the state of senescence. The retinoblastoma (RB) protein has an important role in SAHF; cells that lack active RB pathway fail to form SAHF. It has been known that the posttranslational modifications of RB, for example, phosphorylation, regulate its function. To date, whether methylation of RB impacts on the SAHF formation is unknown. Here we report that JMJD3, a histone demethylase catalyzing the tri-methylation of H3K27 (H3K27me3), can demethylate the non-histone protein RB at the lysine810 residue (K810), which is a target of the methyltransferase Set7/9. We detected a significant upregulation of JMJD3 during cellular senescence and SAHF formation in WI38 cells induced by H-RasV(12), and we found that ectopic expression of JMJD3 promoted cellular senescence and SAHF formation in WI38 cells. Furthermore, during the process of SAHF assembly, JMJD3 was transported to the cytoplasm and interacted with RB through its demethylase domain JmjC. Significantly, our data demonstrated that the JMJD3-mediated demethylation of RB at K810 impeded the interaction of RB with the protein kinase CDK4 and resulted in reduced level of phosphorylation of RB at Serine807/811 (S807/811), implicating an important role of the interplay between the demethylation and phosphorylation of RB in SAHF assembly. This study highlights the role of JMJD3 as a novel inducer of SAHF formation through demethylating RB and provides new insights into the mechanisms of cellular senescence and SAHF assembly.
已知经历癌基因诱导衰老或复制性衰老的原代人成纤维细胞会形成衰老相关异染色质灶（SAHF），其可稳定衰老状态。视网膜母细胞瘤（RB）蛋白在SAHF中起重要作用；缺乏活跃RB通路的细胞无法形成SAHF。已知RB的翻译后修饰，例如磷酸化，可调节其功能。迄今为止，RB的甲基化是否影响SAHF形成尚不清楚。在此我们报告，组蛋白去甲基化酶JMJD3可催化H3K27的三甲基化（H3K27me3），其能使非组蛋白RB在赖氨酸810残基（K810）处发生去甲基化，而K810是甲基转移酶Set7/9的作用靶点。我们检测到在由H-RasV(12)诱导的WI38细胞衰老和SAHF形成过程中，JMJD3显著上调，并且我们发现JMJD3的异位表达促进了WI38细胞的衰老和SAHF形成。此外，在SAHF组装过程中，JMJD3被转运至细胞质并通过其去甲基化酶结构域JmjC与RB相互作用。重要的是，我们的数据表明，JMJD3介导的RB在K810处的去甲基化阻碍了RB与蛋白激酶CDK4的相互作用，并导致RB在丝氨酸807/811（S807/811）处的磷酸化水平降低，这表明RB的去甲基化和磷酸化之间的相互作用在SAHF组装中起重要作用。本研究突出了JMJD3作为通过使RB去甲基化而诱导SAHF形成的新型诱导剂的作用，并为细胞衰老和SAHF组装机制提供了新见解。
