SON-mediated gene expression and leukemia

 描述(申请人提供)：白血病是最常见和最具破坏性的癌症，影响儿童和年轻人，死亡率很高。在白血病患者中发现了许多转录因子、RNA剪接因子和表观遗传修饰物的突变和表达变化，表明基因表达机制失调是白血病的一个特征。SON是一种在血细胞中高度表达的核蛋白，最近发现其在细胞周期和多能性相关基因的RNA剪接中起着关键作用。除了其与RNA结合的能力和作为剪接介体的功能外，SON还被证明可以抑制一些哺乳动物基因的转录。然而，SON介导的转录调控机制和SON功能与疾病的相关性在很大程度上尚不清楚。我们的SON芯片序列分析的初步数据显示，SON与多个基因组位置相互作用，抑制靶基因的转录，这些靶基因包括与造血、干细胞维持和白血病发生相关的关键因子。有趣的是，SON基因敲除导致组蛋白H3(H3K4me3)上赖氨酸4的三甲基化增加，从而引发SON靶向启动子的基因激活。我们还发现含有RNA结合基序的SON的C末端是抑制启动子活性所必需的，并鉴定了几个与SON相互作用的非编码RNA的候选者。更有趣的是，Son E，一种缺乏RNA结合基序的短Son亚型，在白血病中高度表达。此外，SON E在转录抑制中对全长SON的功能表现出明显的负面影响，同时促进了全长SON介导的RNA剪接。根据我们的初步数据，我们假设含有RNA组分的SON复合体通过调节组蛋白修饰来抑制靶基因的激活，而SON E(一种短的异构体)的上调导致SON靶基因表达的改变，并促进造血干细胞的自我更新，从而促进白血病的发生。为了验证这一假说，我们提出了以下具体目标：(1)阐明SON介导的转录抑制的分子机制。(2)探讨SON E上调对造血干细胞基因表达、增殖和自我更新的影响。(3)明确Son E在白血病发生中的作用。研究SON及其短亚型在控制基因表达和白血病发生中的作用，将为微调基因表达的新模式提供有价值的机制见解，并为白血病和其他血液系统恶性肿瘤提供新的治疗靶点。

 DESCRIPTION (provided by applicant): Leukemia is the most common and devastating cancer affecting children and young adults with high mortality rate. Mutations and altered expression of numerous transcription factors, RNA splicing factors and epigenetic modifiers have been identified in leukemia patients, indicating that dysregulation of gene expression machinery is a hallmark of leukemia. SON is a poorly characterized nuclear protein highly expressed in blood cells, and the critical role of SON in RNA splicing of cell cycle- and pluripotency-related genes was recently identified. Besides its RNA-binding ability and the function as a splicing mediator, SON has also been shown to repress transcription of a few mammalian genes. However, the mechanisms of SON-mediated transcriptional regulation and the disease relevance of SON functions are largely unknown. Our preliminary data from SON ChIP-seq analyses revealed that SON interacts with multiple genomic locations to suppress transcription of target genes which include critical factors associated with hematopoiesis, stem cell maintenance and leukemogenesis. Interestingly, SON knockdown results in increased tri-methylation of lysine 4 on histone H3 (H3K4me3), eliciting gene activation at SON-targeted promoters. We also found that the C-terminus of SON containing RNA-binding motifs is necessary to suppress promoter activity, and identified several candidates of SON-interacting non-coding RNAs. More interestingly, SON E, a short SON isoform lacking RNA-binding motifs, is highly expressed in leukemia. In addition, SON E exhibits a dominant negative effect on full-length SON function in transcriptional repression, while enhancing full-length SON-mediated RNA splicing. Based on our preliminary data, we hypothesize that the SON complex containing RNA components suppresses target gene activation through regulating histone modifications, and upregulation of SON E (a short isoform) causes alterations in SON target gene expression and enhances hematopoietic stem cell self-renewal, which facilitates leukemogenesis. To test this hypothesis, we propose following specific aims; (1) To elucidate the molecular mechanisms of SON-mediated transcriptional repression. (2) To investigate the effect of SON E upregulation on gene expression, proliferation and self-renewal in hematopoietic stem cells. (3) To identify the role of SON E in leukemogenesis. Investigation of the function of SON and its short isoform in controlling gene expression and leukemogenesis will generate valuable mechanistic insights into a novel mode of fine-tuning of gene expression, and reveal new therapeutic targets for leukemia and other hematopoietic malignancies.