Lorković Zdravko J, Hilscher Julia, Barta Andrea
Max F. Perutz Laboratories, Medical University of Vienna, Department of Medical Biochemistry, Vienna, Austria.
Exp Cell Res. 2008 Oct 15;314(17):3175-86. doi: 10.1016/j.yexcr.2008.06.020. Epub 2008 Jul 2.
SR proteins are multidomain splicing factors which are important for spliceosome assembly and for regulation of alternative splicing. In mammalian nuclei these proteins localise to speckles from where they are recruited to transcription sites. By using fluorescent protein fusion technology and different experimental approaches it has been shown that Arabidopsis SR proteins, in addition to diffuse nucleoplasmic staining, localise into an irregular nucleoplasmic network resembling speckles in mammalian cells. As Arabidopsis SR proteins fall into seven conserved sub-families we investigated co-localisation of members of the different sub-families in transiently transformed tobacco protoplast. Here we demonstrate the new finding that members of different SR protein sub-families localise into distinct populations of nuclear speckles with no, partial or complete co-localisation. This is particularly interesting as we also show that these proteins do interact in a yeast two-hybrid assay as well as in pull-down and in co-immunopreciptiation assays. Our data raise the interesting possibility that SR proteins are partitioned into distinct populations of nuclear speckles to allow a more specific recruitment to the transcription/pre-mRNA processing sites of particular genes depending on cell type and developmental stage.
SR蛋白是多结构域剪接因子，对剪接体组装和可变剪接调控至关重要。在哺乳动物细胞核中，这些蛋白定位于核斑，从核斑处被招募到转录位点。通过使用荧光蛋白融合技术和不同的实验方法已表明，拟南芥SR蛋白除了弥漫性核质染色外，还定位于类似于哺乳动物细胞中核斑的不规则核质网络中。由于拟南芥SR蛋白分为七个保守亚家族，我们研究了不同亚家族成员在瞬时转化的烟草原生质体中的共定位情况。在此，我们展示了一个新发现，即不同SR蛋白亚家族的成员定位于不同的核斑群体，不存在、部分或完全共定位。这尤其有趣，因为我们还表明这些蛋白在酵母双杂交试验以及下拉和免疫共沉淀试验中确实相互作用。我们的数据提出了一个有趣的可能性，即SR蛋白被分配到不同的核斑群体中，以便根据细胞类型和发育阶段更特异性地招募到特定基因的转录/前体mRNA加工位点。
