Molecular mechanism of oncogenesis by translcated genes encoding chromath remodelhg factors fused to a nucleoporin

本研究的最终目的是阐明染色质重塑因子-核孔蛋白融合基因TAF-I（Template Activating Factor-I）β/SET-CAN和DEK-CAN与髓系白血病相关的肿瘤发生的分子和细胞机制。TAF-Iβ/SET是一种组蛋白伴侣，DEK是一种参与染色质结构调控的因子，CAN是核孔复合物的组成成分之一，Nup 214也被认为是一种重要的核孔复合物。发现TAF-Iβ-CAN以不同的点存在于细胞核中。hCRM 1是一种与CAN结合的输出蛋白，它与TAF-1 β-CAN结合，因此发现hCRM 1的分子靶点内斯蛋白在细胞核中积累。在TAF-1 β-CAN转化的细胞中，用特异性siRNA敲低TAF-1 β-CAN的表达取消了一些细胞转化特性，表明TAF-1 β/SET-CAN通过至少两种独立的机制参与细胞转化。对部分融合基因产物的研究发现：TAF-Iβ/SET与trxG家族成员MLL结合，参与MLL靶基因的表达调控。TAF-Iβ/SET的结构和功能同源物TAF-II/NAP-1通过其核输出调控有丝分裂进程。发现TAF-III是一种组蛋白伴侣，由核磷酸蛋白/B23和RNA分子组成。使用TAF-III活性的显性阴性突变体的实验表明，TAF-III通过其染色质调节活性参与rRNA合成的调节，从而参与细胞生长速率的控制。

The ultimate goal of this study is to clarify the molecular and cellular mechanism of oncogenesis by chromatin remodeling factor-nucleoporin fusion genes such as TAF-I (Template Activating Factor-I) β/SET-CAN and DEK-CAN associated with myeloid leukemia. TAF-Iβ/SET is a histone chaperone and DEK is identified as a factor involved in regulation of the chromatin structure, while CAN, alternatively designated Nup214, is one of components of nuclear pore complexes.Introduction of TAF-Iβ/SET-CAN into normal cells, for instance, NIH3T3 cells resulted in cell transformation and tumor formation in nude mice. TAF-Iβ-CAN was found to be present in the nucleus as distinct dots. hCRM1, an exportin that binds to CAN bound to TAF-Iβ-CAN, so that NES proteins, molecular targets of hCRM1, were found accumulated in the nucleus. Knock-down of expression of TAF-Iβ-CAN in TAF-Iβ-CAN-transformed cells with specific si RNA cancelled some of the cell transformation properties, suggesting that TAF-Iβ/SET-CAN is involved in cell transformation through at least two independent mechanisms. Studies on parts of the fusion gene products revealed several novel findings: TAF-Iβ/SET bound to MLL, a trxG family member, and was found to be involved in expression regulation of MLL target genes with MLL. TAF-II/NAP-1, a structural and functional homologue of TAF-Iβ/SET, regulated the mitotic progression through its nuclear export. It was found that TAF-III, a histone chaperone consists of nucleophosmin/B23 and RNA molecules. Experiments using dominant-negative mutants for the TAF-III activity showed that TAF-III is involved in regulation of rRNA synthesis through its chromatin regulation activity and thereby in cell growth rate control.