Homeodomain-Interacting Protein Kinase 2, a Novel Autoimmune Regulator Interaction Partner, Modulates Promiscuous Gene Expression in Medullary Thymic Epithelial Cells
Homeodomain-Interacting Protein Kinase 2, a Novel Autoimmune Regulator Interaction Partner, Modulates Promiscuous Gene Expression in Medullary Thymic Epithelial Cells
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DOI：
10.4049/jimmunol.1402694
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发表时间：
2015-02-01
影响因子：
4.4
通讯作者：
Derbinski, Jens
中科院分区：
文献类型：
--
作者：
Rattay, Kristin;Claude, Janine;Derbinski, Jens
胸腺髓质上皮细胞（mTECs）混杂表达过多的组织限制性抗原（TRAs）在T细胞耐受中起重要作用。虽然混杂基因表达（pGE）施加T细胞耐受的细胞机制已得到很好的表征，但其潜在的分子机制仍知之甚少。自身免疫调节因子（AIRE）是迄今为止已知的唯一经验证的调节pGE的分子。AIRE是高阶多蛋白复合物的一部分，其促进多种靶基因的转录、延伸和剪接。AIRE及其合作伙伴如何在分子水平上介导这些不同的影响仍然很不清楚。使用酵母双杂交筛选，我们寻找新的AIRE相互作用蛋白，并确定同源域相互作用蛋白激酶2（HIPK2）作为一个新的合作伙伴。HIPK2在共转染时与AIRE部分共定位于核体中，并在人mTEC中原位共定位。此外，HIPK2在体外磷酸化AIRE并以激酶依赖性方式抑制AIRE的共激活因子活性。为了评估Hipk2在体内调节AIRE功能中的作用，我们比较了来自TEC特异性Hipk2敲除小鼠和对照小鼠的纯化mTEC子集的全基因组基因特征，并鉴定了一小部分差异表达基因。出乎意料的是，大多数差异表达的基因仅限于CD80（lo）mTEC亚群，并优先包括AIRE非依赖性TRA。因此，尽管它调节mTECs中的基因表达，并且还影响髓腔的大小，但TEC特异性HIPK2缺失仅在体内轻微影响AIRE指导的pGE。
Promiscuous expression of a plethora of tissue-restricted Ags (TRAs) by medullary thymic epithelial cells (mTECs) plays an essential role in T cell tolerance. Although the cellular mechanisms by which promiscuous gene expression (pGE) imposes T cell tolerance have been well characterized, the underlying molecular mechanisms remain poorly understood. The autoimmune regulator (AIRE) is to date the only validated molecule known to regulate pGE. AIRE is part of higher-order multiprotein complexes, which promote transcription, elongation, and splicing of a wide range of target genes. How AIRE and its partners mediate these various effects at the molecular level is still largely unclear. Using a yeast two-hybrid screen, we searched for novel AIRE-interacting proteins and identified the homeodomain-interacting protein kinase 2 (HIPK2) as a novel partner. HIPK2 partially colocalized with AIRE in nuclear bodies upon cotransfection and in human mTECs in situ. Moreover, HIPK2 phosphorylated AIRE in vitro and suppressed the coactivator activity of AIRE in a kinase-dependent manner. To evaluate the role of Hipk2 in modulating the function of AIRE in vivo, we compared whole-genome gene signatures of purified mTEC subsets from TEC-specific Hipk2 knockout mice with control mice and identified a small set of differentially expressed genes. Unexpectedly, most differentially expressed genes were confined to the CD80(lo) mTEC subset and preferentially included AIRE-independent TRAs. Thus, although it modulates gene expression in mTECs and in addition affects the size of the medullary compartment, TEC-specific HIPK2 deletion only mildly affects AIRE-directed pGE in vivo.