Transcriptional repressor germ cell-less (GCL) and barrier to autointegration factor (BAF) compete for binding to emerin in vitro
Transcriptional repressor germ cell-less (GCL) and barrier to autointegration factor (BAF) compete for binding to emerin in vitro
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DOI：
10.1074/jbc.m208811200
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发表时间：
2003-02-28
影响因子：
4.8
通讯作者：
Wilson, KL
中科院分区：
文献类型：
--
作者：
Holaska, JM;Lee, KK;Wilson, KL
Emerin属于核蛋白的LEM结构域家族，含有一个与LEM结构域相似的40个氨基酸残基。LEM结构域介导与自整合因子（BAF）的直接结合，BAF是秀丽隐杆线虫胚胎发生所必需的保守的10 kDa染色质蛋白。在哺乳动物细胞中，BAF在核组装过程中将Emerin招募到染色质中。BAF还在核组装期间介导染色质解凝聚。Emerin的LEM结构域和中心区域分别是与BAF和核纤层蛋白A结合所必需的。然而，另外两个保守的区域emerin缺乏归属的功能，这表明emerin可能有额外的合作伙伴。我们发现，这些“未归属”的结构域的emerin介导直接结合到一个转录抑制因子，生殖细胞（GCL）。GCL与来自HeLa细胞的Emerin共免疫沉淀。我们确定了Emerin对GCL、BAF和核纤层蛋白A的结合亲和力，并分析了它们的寡聚相互作用。我们发现，emerin形成稳定的复合物与核纤层蛋白A加GCL或核纤层蛋白A加BAF。重要的是，BAF与GCL竞争体外结合Emerin，预测Emerin在体内可以形成至少两种不同类型的复合物。Emerin的缺失导致Emery-Dreifuss肌营养不良症，这是一种影响骨骼肌、主要肌腱和心脏传导系统的组织特异性遗传性疾病。虽然GCL不能单独解释的疾病机制，我们的研究结果强烈支持Emery-Dreifuss肌营养不良症的基因表达模型，表明Emerin直接结合到转录抑制因子，GCL，并建议Emerin抑制复合物可能受到BAF的调节。生化Emerin基因表达的作用进行了讨论。
Emerin belongs to the "LEM domain" family of nuclear proteins, which contain a characteristic similar to40-residue LEM motif. The LEM domain mediates direct binding to barrier to autointegration factor (BAF), a conserved 10-kDa chromatin protein essential for embryogenesis in Caenorhabditis elegans. In mammalian cells, BAF recruits emerin to chromatin during nuclear assembly. BAF also mediates chromatin decondensation during nuclear assembly. The LEM domain and central region of emerin are essential for binding to BAF and lamin A, respectively. However, two other conserved regions of emerin lacked ascribed functions, suggesting that emerin could have additional partners. We discovered that these "unascribed" domains of emerin mediate direct binding to a transcriptional repressor, germ cell-less (GCL). GCL co-immunoprecipitates with emerin from HeLa cells. We determined the binding affinities of emerin for GCL, BAF, and lamin A and analyzed their oligomeric interactions. We showed that emerin forms stable complexes with either lamin A plus GCL or lamin A plus BAF. Importantly, BAF competed with GCL for binding to emerin in vitro, predicting that emerin can form at least two distinct types of complexes in vivo. Loss of emerin causes Emery-Dreifuss muscular dystrophy, a tissue-specific inherited disease that affects skeletal muscles, major tendons, and the cardiac conduction system. Although GCL alone cannot explain the disease mechanism, our results strongly support gene expression models for Emery-Dreifuss muscular dystrophy by showing that emerin binds directly to a transcriptional repressor, GCL, and by suggesting that emerin-repressor complexes might be regulated by BAF. Biochemical roles for emerin in gene expression are discussed.