Hoke Stephen M T, Guzzo Julie, Andrews Brenda, Brandl Christopher J
Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, N6A 5C1, Canada.
BMC Genet. 2008 Jul 10;9:46. doi: 10.1186/1471-2156-9-46.
Tra1 is an essential 437-kDa component of the Saccharomyces cerevisiae SAGA/SLIK and NuA4 histone acetyltransferase complexes. It is a member of a group of key signaling molecules that share a carboxyl-terminal domain related to phosphatidylinositol-3-kinase but unlike many family members, it lacks kinase activity. To identify genetic interactions for TRA1 and provide insight into its function we have performed a systematic genetic array analysis (SGA) on tra1SRR3413, an allele that is defective in transcriptional regulation.
The SGA analysis revealed 114 synthetic slow growth/lethal (SSL) interactions for tra1SRR3413. The interacting genes are involved in a range of cellular processes including gene expression, mitochondrial function, and membrane sorting/protein trafficking. In addition many of the genes have roles in the cellular response to stress. A hierarchal cluster analysis revealed that the pattern of SSL interactions for tra1SRR3413 most closely resembles deletions of a group of regulatory GTPases required for membrane sorting/protein trafficking. Consistent with a role for Tra1 in cellular stress, the tra1SRR3413 strain was sensitive to rapamycin. In addition, calcofluor white sensitivity of the strain was enhanced by the protein kinase inhibitor staurosporine, a phenotype shared with the Ada components of the SAGA/SLIK complex. Through analysis of a GFP-Tra1 fusion we show that Tra1 is principally localized to the nucleus.
We have demonstrated a genetic association of Tra1 with nuclear, mitochondrial and membrane processes. The identity of the SSL genes also connects Tra1 with cellular stress, a result confirmed by the sensitivity of the tra1SRR3413 strain to a variety of stress conditions. Based upon the nuclear localization of GFP-Tra1 and the finding that deletion of the Ada components of the SAGA complex result in similar phenotypes as tra1SRR3413, we suggest that the effects of tra1SRR3413 are mediated, at least in part, through its role in the SAGA complex.
Tra1是酿酒酵母SAGA/SLIK和NuA4组蛋白乙酰转移酶复合物中一个重要的437 kDa组分。它是一组关键信号分子的成员，这些分子共享一个与磷脂酰肌醇-3-激酶相关的羧基末端结构域，但与许多家族成员不同的是，它缺乏激酶活性。为了确定TRA1的遗传相互作用并深入了解其功能，我们对tra1SRR3413进行了系统遗传阵列分析（SGA），该等位基因在转录调控方面存在缺陷。
SGA分析揭示了tra1SRR3413的114种合成性生长缓慢/致死（SSL）相互作用。相互作用的基因涉及一系列细胞过程，包括基因表达、线粒体功能以及膜分选/蛋白质运输。此外，许多基因在细胞应激反应中发挥作用。层次聚类分析表明，tra1SRR3413的SSL相互作用模式与膜分选/蛋白质运输所需的一组调节性GTP酶的缺失最为相似。与Tra1在细胞应激中的作用一致，tra1SRR3413菌株对雷帕霉素敏感。此外，蛋白激酶抑制剂星形孢菌素增强了该菌株对荧光增白剂的敏感性，这是SAGA/SLIK复合物的Ada组分共有的一种表型。通过对GFP-Tra1融合蛋白的分析，我们表明Tra1主要定位于细胞核。
我们已经证明Tra1与核、线粒体和膜过程存在遗传关联。SSL基因的身份也将Tra1与细胞应激联系起来，tra1SRR3413菌株对多种应激条件的敏感性证实了这一结果。基于GFP-Tra1的核定位以及SAGA复合物的Ada组分缺失导致与tra1SRR3413相似表型的发现，我们认为tra1SRR3413的作用至少部分是通过其在SAGA复合物中的作用介导的。
