Batlle Marta, Marsellach Francesc-Xavier, Huertas Dori, Azorín Fernando
Institute of Molecular Biology of Barcelona, CSIC, Institute for Research in Biomedicine (IRB Barcelona), Barcelona Science Park, Baldiri Rexac, 12, 08028 Barcelona, Spain.
Biochim Biophys Acta. 2011 Jan;1809(1):46-55. doi: 10.1016/j.bbagrm.2010.10.005. Epub 2010 Oct 28.
Functional characterisation of vigilin, a highly conserved multi-KH-domain protein that binds RNA and ssDNA, remains elusive and, to some extent, controversial. Studies performed in Saccharomyces cerevisiae and human cells indicate that vigilin localises to the cytoplasm, binds ribosomes, associates to RER and regulates mRNA translation. On the other hand, we and others reported a contribution to heterochromatin-mediated gene silencing (PEV) and chromosome segregation in S. cerevisiae, Drosophila and human cells. Whether this contribution is direct remains, however, unclear. Here, we report that Drosophila vigilin, DDP1, vastly localises to the cytoplasm, being largely excluded from the nucleus. We also show that DDP1 preferentially associates to RER and co-purifies with several ribosomal proteins, suggesting a contribution to mRNA translation. In light of these results, the contribution of DDP1 to PEV was re-examined. Here, we show that a newly generated null ddp1(Δ) mutation is only a weak suppressor of PEV, which is in contrast with our own previous results showing dominant suppression in the presence of a strong hypomorphic ddp1(15.1) mutation. Similar results were obtained in the fission yeast Schizosaccharomyces pombe, where vigilin (Vgl1) also associates to RER, having no significant contribution to PEV at centromeres, telomeres and the mating-type locus. Altogether, these results indicate that cytoplasmic localisation and association to RER, but not contribution to heterochromatin organisation, are evolutionarily conserved features of vigilin, favouring a model by which vigilin acts in the cytoplasm, regulating RNA metabolism, and affects nuclear functions only indirectly.
维吉林是一种高度保守的多KH结构域蛋白，可结合RNA和单链DNA，其功能特性仍不清楚，在某种程度上还存在争议。在酿酒酵母和人类细胞中进行的研究表明，维吉林定位于细胞质，结合核糖体，与粗面内质网相关，并调节mRNA翻译。另一方面，我们和其他人报道了维吉林在酿酒酵母、果蝇和人类细胞中对异染色质介导的基因沉默（位置效应斑驳，PEV）和染色体分离有作用。然而，这种作用是否直接尚不清楚。在这里，我们报道果蝇维吉林DDP1主要定位于细胞质，基本排除在细胞核之外。我们还表明，DDP1优先与粗面内质网相关，并与几种核糖体蛋白共纯化，表明其对mRNA翻译有作用。鉴于这些结果，我们重新研究了DDP1对PEV的作用。在这里，我们表明新产生的ddp1(Δ)无效突变只是PEV的弱抑制子，这与我们之前的结果相反，我们之前的结果显示在存在强亚效等位基因ddp1(15.1)突变时具有显性抑制作用。在裂殖酵母粟酒裂殖酵母中也获得了类似的结果，在那里维吉林（Vgl1）也与粗面内质网相关，在着丝粒、端粒和交配型位点对PEV没有显著作用。总之，这些结果表明，细胞质定位和与粗面内质网的关联，而非对异染色质组织的作用，是维吉林在进化上保守的特征，这支持了一种模型，即维吉林在细胞质中起作用，调节RNA代谢，仅间接影响核功能。
