The Unkempt RNA binding protein reveals a local translation program in centriole overduplication

Excess centrosomes cause defects in mitosis, cell-signaling, and cell migration, and therefore their assembly is tightly regulated. The divergent Polo kinase, PLK4, controls centriole duplication at the heart of centrosome assembly, and elevated PLK4 levels promote centrosome amplification (CA), a founding event of tumorigenesis. Here, we investigate the transcriptional consequences of elevated PLK4 and find Unkempt (UNK), a gene encoding an RNA binding protein with roles in mRNA translational regulation, to be one of only two upregulated mRNAs. UNK protein localizes to centrosomes and CEP131-positive centriolar satellites and promotes CEP131 localization to and around centrosomes. UNK's RNA binding activity is required for PLK4-induced centriole overduplication. Consistent with the loss in PLK4-induced centriole overduplication, UNK depletion disrupts PLK4 and centriole assembly protein localization. Finally, translation is enriched at centrosomes and centriolar satellites with UNK and CEP131 promoting this localized translation. In summary, UNK and CEP131 promote PLK4 localization and local translation at centrosomes during centriole overduplication. Analysis of gene expression changes using RNA-seq after overexpression of PLK4 in RPE-1 cells *************************************************************** The table below lists GEO accessions reused/reanalyzed for this study. ***************************************************************

过量中心体（centrosome）会引发有丝分裂（mitosis）、细胞信号转导（cell-signaling）与细胞迁移（cell migration）异常，故其组装过程受到严格调控。异型Polo激酶（Polo kinase）PLK4（Polo-like kinase 4）是中心体组装（centrosome assembly）核心环节中调控中心粒复制（centriole duplication）的关键因子，其表达水平升高会促进中心体扩增（centrosome amplification, CA）——这是肿瘤发生（tumorigenesis）的起始事件。本研究探究了PLK4过表达带来的转录组改变（transcriptional consequences），发现Unkempt（UNK）基因——其编码一种参与mRNA翻译调控（mRNA translational regulation）的RNA结合蛋白（RNA binding protein）——是仅有的两个上调mRNA（upregulated mRNA）之一。UNK蛋白可定位于中心体以及CEP131阳性中心粒卫星（CEP131-positive centriolar satellites），并促进CEP131向中心体及其周边区域定位。UNK的RNA结合活性（RNA binding activity）是PLK4诱导中心粒过度复制（centriole overduplication）所必需的。与PLK4诱导的中心粒过度复制受损表型一致，敲低UNK会破坏PLK4及中心体组装蛋白的定位。进一步研究发现，翻译过程在中心体与中心粒卫星处存在富集，且UNK与CEP131可促进这一局部翻译过程。综上所述，在中心粒过度复制过程中，UNK与CEP131可促进PLK4在中心体的定位以及局部翻译。本研究通过在RPE-1细胞（RPE-1 cells）中过表达PLK4后，利用RNA测序（RNA-seq）分析基因表达变化。
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下表列出了本研究复用/重新分析的GEO登录号（GEO accession）数据集。
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