Cajal-body formation correlates with differential coilin phosphorylation in primary and transformed cell lines
Cajal-body formation correlates with differential coilin phosphorylation in primary and transformed cell lines
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DOI：
10.1242/jcs.044040
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发表时间：
2009-06-01
影响因子：
4
通讯作者：
Hebert, Michael D.
中科院分区：
文献类型：
--
作者：
Hearst, Scoty M.;Gilder, Andrew S.;Hebert, Michael D.
Cajal小体（CB）被认为具有多种功能，包括小核核糖核蛋白（snRNP）的生物合成。卷曲蛋白（CB标记蛋白）的磷酸化状态可能会影响CB的形成。我们假设，原代细胞，其中缺乏CB，含有不同的磷酸化亚型的卷曲蛋白相比，发现在转化细胞，其中有CB。定位，自缔合和荧光恢复后的光漂白（FRAP）的研究coilin磷酸突变体都表明这种修改影响coilin的功能，因此可能有助于CB的形成。双向凝胶电泳结果表明，原代细胞与转化细胞相比，卷曲蛋白过度磷酸化。核磷酸酶PPM1G的mRNA水平在原代细胞中显著降低，并且原代细胞中PPM1G的表达诱导CB。此外，PPM1G可以在体外使卷曲蛋白去磷酸化。然而，令人惊讶的是，单独表达绿色荧光蛋白足以在原代细胞中形成CB。两者合计，我们的数据支持一个模型，其中卷曲蛋白是一个未表征的信号转导级联反应的目标，增加转录和snRNP的需求中发现的转化细胞。
Cajal bodies (CBs) are nuclear structures that are thought to have diverse functions, including small nuclear ribonucleoprotein (snRNP) biogenesis. The phosphorylation status of coilin, the CB marker protein, might impact CB formation. We hypothesize that primary cells, which lack CBs, contain different phosphoisoforms of coilin compared with that found in transformed cells, which have CBs. Localization, self-association and fluorescence recovery after photobleaching (FRAP) studies on coilin phosphomutants all suggest this modification impacts the function of coilin and may thus contribute towards CB formation. Two-dimensional gel electrophoresis demonstrates that coilin is hyperphosphorylated in primary cells compared with transformed cells. mRNA levels of the nuclear phosphatase PPM1G are significantly reduced in primary cells and expression of PPM1G in primary cells induces CBs. Additionally, PPM1G can dephosphorylate coilin in vitro. Surprisingly, however, expression of green fluorescent protein alone is sufficient to form CBs in primary cells. Taken together, our data support a model whereby coilin is the target of an uncharacterized signal transduction cascade that responds to the increased transcription and snRNP demands found in transformed cells.