Toxicity of human adenovirus E4orf4 protein in Saccharomyces cerevisiae results from interactions with the Cdc55 regulatory B subunit of PP2A
Toxicity of human adenovirus E4orf4 protein in Saccharomyces cerevisiae results from interactions with the Cdc55 regulatory B subunit of PP2A
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DOI：
10.1038/sj.onc.1204693
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发表时间：
2001-08-30
期刊：
影响因子：
8
通讯作者：
Branton, PE
中科院分区：
文献类型：
--
作者：
Roopchand, DE;Lee, JM;Branton, PE
人腺病毒的E4orf4蛋白诱导P53非依赖性的细胞凋亡，这一过程可能促进细胞死亡和病毒传播。单独表达时，E4orf4会杀死转化的细胞，但不会杀死正常的人类细胞。E4orf4在哺乳动物细胞中唯一明确的靶点是蛋白磷酸酶2A(PP2A)的BA(B55)亚基，它是三类调节B亚基之一。在这里，我们报道了E4orf4在酿酒酵母中的作用，它编码两个PP2A调节B亚基，CDC55和RTS1，分别与哺乳动物的B和B‘亚基有同源性。E4orf4在酵母中的表达是有毒的，导致在去除E4orf4后不能生长的G2/M期细胞积累。表达E4orf4的酵母也表现出与cdc55缺失菌株相似的拉长细胞形态。E4orf4需要CDC55才能发挥作用，而RTS1则是必不可少的。E4orf4对PP2A全酶的募集完全依赖于CDC55。这些研究表明，E4orf4诱导哺乳动物细胞的凋亡和酵母细胞的死亡需要与PP2A的B-型亚单位的功能相互作用。然而，在CDC55菌株和与CDC55不相互作用的E4orf4突变体中观察到E4orf4对细胞生长有一定的抑制作用，这表明E4orf4可能具有第二个影响细胞生长的CDC55不依赖的功能。
The E4orf4 protein of human adenovirus induces p53-independent apoptosis, a process that may promote cell death and viral spread. When expressed alone, E4orf4 kills transformed cells but not normal human cells. The only clear target of E4orf4 in mammalian cells is the Ba (B55) subunit of protein phosphatase 2A (PP2A), a member of one of three classes of regulatory B subunits. Here we report the effects of E4orf4 in Saccharomyces cerevisiae, which encodes two PP2A regulatory B subunits, CDC55 and RTS1, that share homology with mammalian B and B' subunits, respectively. E4orf4 expression was found to be toxic in yeast, resulting in the accumulation of cells in G2/M phase that failed to grow upon removal of E4orf4. E4orf4-expressing yeast also displayed an elongated cell morphology similar to cdc55 deletion strains. E4orf4 required CDC55 to elicit its effect, whereas RTS1 was dispensable. The recruitment of the PP2A holoenzyme by E4orf4 was entirely dependent on Cdc55. These studies indicate that E4orf4-induced apoptosis in mammalian cells and cell death in yeast require functional interactions with B-type subunits of PP2A. However, some inhibition of growth by E4orf4 was observed in the cdc55 strain and with an E4orf4 mutant that fails to interact with Cdc55, indicating that E4orf4 may possess a second Cdc55-independent function affecting cell growth.