Jolly C, Vourc'h C, Robert-Nicoud M, Morimoto R I
Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208, USA.
J Cell Biol. 1999 Jun 14;145(6):1133-43. doi: 10.1083/jcb.145.6.1133.
The cell nucleus is organized as discrete domains, often associated with specific events involved in chromosome organization, replication, and gene expression. We have examined the spatial and functional relationship between the sites of heat shock gene transcription and the speckles enriched in splicing factors in primary human fibroblasts by combining immunofluorescence and fluorescence in situ hybridization (FISH). The hsp90alpha and hsp70 genes are inducibly regulated by exposure to stress from a low basal level to a high rate of transcription; additionally the hsp90alpha gene contains 10 introns whereas the hsp70 gene is intronless. At 37 degrees C, only 30% of hsp90alpha transcription sites are associated with speckles whereas little association is detected with the hsp70 gene, whose constitutive expression is undetectable relative to the hsp90alpha gene. Upon exposure of cells to heat shock, the heavy metal cadmium, or the amino acid analogue azetidine, transcription at the hsp90alpha and hsp70 gene loci is strongly induced, and both hsp transcription sites become associated with speckles in >90% of the cells. These results reveal a clear disconnection between the presence of intervening sequences at specific gene loci and the association with splicing factor-rich regions and suggest that subnuclear structures containing splicing factors are associated with sites of transcription.
细胞核被组织成离散的结构域，通常与染色体组织、复制和基因表达中涉及的特定事件相关。我们通过结合免疫荧光和荧光原位杂交（FISH），研究了原代人成纤维细胞中热休克基因转录位点与富含剪接因子的斑点之间的空间和功能关系。hsp90α和hsp70基因受到应激诱导调控，从低基础水平转录到高转录速率；此外，hsp90α基因包含10个内含子，而hsp70基因无内含子。在37℃时，只有30%的hsp90α转录位点与斑点相关，而hsp70基因几乎没有检测到相关性，其组成型表达相对于hsp90α基因难以检测到。当细胞暴露于热休克、重金属镉或氨基酸类似物氮杂环丁烷时，hsp90α和hsp70基因位点的转录被强烈诱导，并且在>90%的细胞中，两个hsp转录位点都与斑点相关。这些结果揭示了特定基因位点上间隔序列的存在与富含剪接因子区域的相关性之间存在明显的脱节，并表明含有剪接因子的亚核结构与转录位点相关。
