Friend Lexie R, Han Siew Ping, Rothnagel Joseph A, Smith Ross
School of Molecular and Microbial Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
Biochim Biophys Acta. 2008 Oct;1783(10):1972-80. doi: 10.1016/j.bbamcr.2008.05.021. Epub 2008 Jun 6.
The heterogeneous nuclear ribonucleoproteins A1, A2/B1 and A3 (hnRNPs A/B) are involved in many nuclear functions that are confined to distinct regions within the nucleus. To characterise and compare the distribution of the hnRNPs A/B in these subnuclear compartments, their colocalisation with spliceosomal components, nascent transcripts and other nuclear markers in HeLa cells was investigated by immunostaining and transfection of GFP constructs. The mechanisms of this localisation were further explored by treating cells with detergent, nucleases and transcription inhibitors. We have also examined the dynamics of A2/B1 throughout the cell cycle. Our results show that hnRNPs A/B have different subnuclear localisations, with A1 differentially localised to the nuclear envelope, and A2/B1 and A3 enriched around nucleoli. This pattern of distribution was dependent on RNA integrity and active transcription. The hnRNPs A/B preferentially colocalised with a subset of splicing factors. Significantly, only rarely did transcription factories colocalise with high levels of these hnRNPs. Moreover, localisation of A2/B1 changed with cell cycle stage. Our findings show that the subnuclear localisation of the hnRNPs A/B is differentially, spatially and temporally regulated, and suggest that this localisation may be relevant to their nuclear functions.
不均一核核糖核蛋白A1、A2/B1和A3（hnRNPs A/B）参与许多局限于细胞核内不同区域的核功能。为了表征和比较hnRNPs A/B在这些核内亚区室中的分布，通过免疫染色和绿色荧光蛋白（GFP）构建体转染，研究了它们在HeLa细胞中与剪接体成分、新生转录本及其他核标记物的共定位情况。通过用去污剂、核酸酶和转录抑制剂处理细胞，进一步探究了这种定位的机制。我们还研究了A2/B1在整个细胞周期中的动态变化。我们的结果表明，hnRNPs A/B具有不同的核内亚定位，A1差异定位于核膜，而A2/B1和A3在核仁周围富集。这种分布模式取决于RNA完整性和活跃转录。hnRNPs A/B优先与一部分剪接因子共定位。值得注意的是，转录工厂很少与这些hnRNPs的高水平共定位。此外，A2/B1的定位随细胞周期阶段而变化。我们的研究结果表明，hnRNPs A/B的核内亚定位在空间和时间上受到差异调节，并且表明这种定位可能与其核功能相关。
