Kämpjärvi Kati, Park Min Ju, Mehine Miika, Kim Nam Hee, Clark Alison D, Bützow Ralf, Böhling Tom, Böhm Jan, Mecklin Jukka-Pekka, Järvinen Heikki, Tomlinson Ian P M, van der Spuy Zephne M, Sjöberg Jari, Boyer Thomas G, Vahteristo Pia
Department of Medical Genetics, Genome-Scale Biology Research Program, University of Helsinki, Helsinki, Finland.
Hum Mutat. 2014 Sep;35(9):1136-41. doi: 10.1002/humu.22612. Epub 2014 Jul 21.
Mediator regulates transcription by connecting gene-specific transcription factors to the RNA polymerase II initiation complex. We recently discovered by exome sequencing that specific exon 2 mutations in mediator complex subunit 12 (MED12) are extremely common in uterine leiomyomas. Subsequent screening studies have focused on this mutational hot spot, and mutations have been detected in uterine leiomyosarcomas, extrauterine leiomyomas and leiomyosarcomas, endometrial polyps, and colorectal cancers. All mutations have been missense changes or in-frame insertions/deletions. Here, we have analyzed 611 samples representing all above-mentioned tumor types for possible exon 1 mutations. Five mutations were observed, all of which were in-frame insertion/deletions in uterine leiomyomas. Transcriptome-wide expression data revealed that MED12 exon 1 and exon 2 mutations lead to the same unique global gene expression pattern with RAD51B being the most upregulated gene. Immunoprecipitation and kinase activity assays showed that both exon 1 and exon 2 mutations disrupt the interaction between MED12 and Cyclin C and CDK8/19 and abolish the mediator-associated CDK kinase activity. These results further emphasize the role of MED12 in uterine leiomyomas, show that exon 1 and exon 2 exert their tumorigenic effect in similar manner, and stress that exon 1 should be included in subsequent MED12 screenings.
中介体通过将基因特异性转录因子与RNA聚合酶II起始复合物相连来调节转录。我们最近通过外显子组测序发现，中介体复合物亚基12（MED12）中的特定外显子2突变在子宫平滑肌瘤中极为常见。随后的筛查研究聚焦于这个突变热点，并且在子宫平滑肌肉瘤、子宫外平滑肌瘤和平滑肌肉瘤、子宫内膜息肉以及结直肠癌中都检测到了突变。所有突变均为错义改变或框内插入/缺失。在此，我们分析了代表上述所有肿瘤类型的611个样本，以寻找可能的外显子1突变。观察到5个突变，所有这些突变均为子宫平滑肌瘤中的框内插入/缺失。全转录组表达数据显示，MED12外显子1和外显子2突变导致相同的独特全局基因表达模式，其中RAD51B是上调最明显的基因。免疫沉淀和激酶活性测定表明，外显子1和外显子2突变均破坏了MED12与细胞周期蛋白C以及CDK8/19之间的相互作用，并消除了与中介体相关的CDK激酶活性。这些结果进一步强调了MED12在子宫平滑肌瘤中的作用，表明外显子1和外显子2以相似的方式发挥其致瘤作用，并强调外显子1应纳入后续的MED12筛查中。
