Melanoma-associated mutations in protein phosphatase 6 cause chromosome instability and DNA damage owing to dysregulated Aurora-A
Melanoma-associated mutations in protein phosphatase 6 cause chromosome instability and DNA damage owing to dysregulated Aurora-A
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DOI：
10.1242/jcs.128397
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发表时间：
2013-08-01
影响因子：
4
通讯作者：
Barr, Francis A.
中科院分区：
文献类型：
--
作者：
Hammond, Dean;Zeng, Kang;Barr, Francis A.
蛋白磷酸酶6（PP 6）PPP 6C催化亚基的突变是黑色素瘤发展的驱动因素。在这里，我们分析了一组与黑素瘤相关的PPP 6C突变，发现这些突变通常会损害PP 6全酶的组装和对模型底物的催化活性。对原发性黑色素瘤和工程细胞系中的一种突变体PPP 6C-H114 Y的详细分析表明，它是不稳定的，并且经历了增加的蛋白酶体介导的周转。通过质谱法对磷酸酶底物进行全局分析，确定致癌激酶Aurora-A是在这些条件下失调的主要PP 6底物。因此，缺乏PPP 6C或携带PPP 6C-H114 Y等位基因的细胞具有升高的Aurora-A激酶活性，并显示染色体不稳定性和相关的Aurora-A依赖性微核。与这些微核错误分离的染色体优先被DNA损伤标记物γ-H2 AX染色，表明PPP 6C的缺失促进了染色体不稳定性和DNA损伤。这些发现支持了这样的观点，即微核的形成而不是染色体不稳定性单独解释了PPP 6C的丢失，以及更普遍的有丝分裂纺锤体和中心体缺陷如何成为黑色素瘤和其他癌症中基因组不稳定性的驱动因素。
Mutations in the PPP6C catalytic subunit of protein phosphatase 6 (PP6) are drivers for the development of melanoma. Here, we analyse a panel of melanoma-associated mutations in PPP6C and find that these generally compromise assembly of the PP6 holoenzyme and catalytic activity towards a model substrate. Detailed analysis of one mutant, PPP6C-H114Y, in both primary melanoma and engineered cell lines reveals it is destabilized and undergoes increased proteasome-mediated turnover. Global analysis of phosphatase substrates by mass spectrometry identifies the oncogenic kinase Aurora-A as the major PP6 substrate that is dysregulated under these conditions. Accordingly, cells lacking PPP6C or carrying the PPP6C-H114Y allele have elevated Aurora-A kinase activity and display chromosome instability with associated Aurora-A-dependent micronucleation. Chromosomes mis-segregated to these micronuclei are preferentially stained by the DNA damage marker gamma-H2AX, suggesting that loss of PPP6C promotes both chromosome instability and DNA damage. These findings support the view that formation of micronuclei rather than chromosome instability alone explains how loss of PPP6C, and more generally mitotic spindle and centrosome defects, can act as drivers for genome instability in melanoma and other cancers.