背景:多发性内分泌肿瘤1型(MEN1)基因的功能缺失突变是MEN1肿瘤综合征的原因,但它们也常见于散发性胰腺神经内分泌肿瘤和其他类型的癌症。MEN1基因产物,梅宁,参与转录和染色质调节,最重要的是作为含有COMPASS样组蛋白H3K4甲基转移酶复合物的KMT2A/MLL1和KMT2B/MLL2的组成部分。以一种相互排斥的方式,menin还与AP-1的JunD亚基和ATF/CREB转录因子相互作用。
结果:这里,我们对253个疾病相关MEN1错义突变进行了计算机筛选,以筛选出一组9个表面暴露残基中的menin突变.通过定量质谱法评估这些突变体的蛋白质相互作用,这表明9个突变体中有7个破坏了与MLL1/MLL2和JunD复合物的相互作用。有趣的是,我们发现了三个错义突变,R52G,E255K和E359K,与JunD相比,主要减少MLL1和MLL2相互作用。R52G结合的明显丧失支持了这一观察结果。E255K和E359K突变蛋白在独特的MLL1基因组结合位点,对独特的JunD位点影响较小。
结论:我们的结果强调了内分泌起源的家族性和散发性肿瘤中MEN1基因突变对menin与MLL1和MLL2组蛋白H3K4甲基转移酶复合物以及含有JunD的转录因子相互作用的影响。Menin结合口袋突变体R52G,E255K和E359K对MLL1/MLL2和JunD相互作用有不同的影响,转化为差异基因组结合模式。我们的发现鼓励未来研究解决MEN1疾病模型系统中menin突变体的单独MLL1/MLL2-和JunD依赖性功能的病理生理学相关性。
BACKGROUND: Loss-of-function mutations of the multiple endocrine neoplasia type 1 (MEN1) gene are causal to the MEN1 tumor syndrome, but they are also commonly found in sporadic pancreatic neuroendocrine tumors and other types of cancers. The MEN1 gene product, menin, is involved in transcriptional and chromatin regulation, most prominently as an integral component of KMT2A/MLL1 and KMT2B/MLL2 containing COMPASS-like histone H3K4 methyltransferase complexes. In a mutually exclusive fashion, menin also interacts with the JunD subunit of the AP-1 and ATF/CREB transcription factors.
RESULTS: Here, we applied and in silico screening approach for 253 disease-related MEN1 missense mutations in order to select a set of nine menin mutations in surface-exposed residues. The protein interactomes of these mutants were assessed by quantitative mass spectrometry, which indicated that seven of the nine mutants disrupt interactions with both MLL1/MLL2 and JunD complexes. Interestingly, we identified three missense mutations, R52G, E255K and E359K, which predominantly reduce the MLL1 and MLL2 interactions when compared with JunD. This observation was supported by a pronounced loss of binding of the R52G, E255K and E359K mutant proteins at unique MLL1 genomic binding sites with less effect on unique JunD sites.
CONCLUSIONS: Our results underline the effects of MEN1 gene mutations in both familial and sporadic tumors of endocrine origin on the interactions of menin with the MLL1 and MLL2 histone H3K4 methyltransferase complexes and with JunD-containing transcription factors. Menin binding pocket mutants R52G, E255K and E359K have differential effects on MLL1/MLL2 and JunD interactions, which translate into differential genomic binding patterns. Our findings encourage future studies addressing the pathophysiological relevance of the separate MLL1/MLL2- and JunD-dependent functions of menin mutants in MEN1 disease model systems.