Protein phosphatase PP6N terminal domain restricts G1 to S phase progression in human cancer cells
Protein phosphatase PP6N terminal domain restricts G1 to S phase progression in human cancer cells
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DOI：
10.4161/cc.6.11.4276
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发表时间：
2007-06-01
期刊：
影响因子：
4.3
通讯作者：
Brautigan, David L.
中科院分区：
文献类型：
--
作者：
Stefansson, Bjarki;Brautigan, David L.
酵母 SIT4 是一个必需基因，编码在真核进化过程中保守的丝氨酸/苏氨酸磷酸酶蛋白，在果蝇中称为 PPV，在脊椎动物中称为 PP6。 Sit4 促进 G(1) 细胞周期蛋白的转录，并且 sat4(ts) 菌株在限制性温度下表现出 G1 停滞。通过表达PPV或含有与果蝇PP1融合的PPV前53个残基的嵌合磷酸酶，酵母sit4ts被拯救。结果表明，Sit4/PPV 蛋白的 N 末端在酵母细胞周期中发挥特定功能。在这里，我们测试了人 PP6 的 N 末端是否对人细胞中的 G(1)-S 进程产生特定影响。 PP6 或 PP2A 的 N 末端与 GFP 融合，蛋白质在前列腺癌 PC-3 细胞中瞬时表达。 PP6 融合蛋白的表达被限制在低于 PP2A 融合蛋白或 GFP 的水平。然而，PP6融合蛋白阻止进入S期并使G1期细胞的比例增加>20%。 PP6融合蛋白的表达没有显着改变细胞周期蛋白或ca的转录物水平。 80 个其他细胞周期基因，但确实抑制了 G1 期细胞中细胞周期蛋白 D1 蛋白的水平，并减少了 RB1 Ser807/811 的磷酸化。因此，我们的结果提供了证据，证明 PP6 至少部分通过控制细胞周期蛋白 D1 来调节人类细胞的细胞周期进程，并且 PP6 的功能与其在酵母中的同源物 Sit4 不同。
Yeast SIT4 is an essential gene encoding a protein Ser/Thr phosphatase conserved throughout eukaryotic evolution, known as PPV in Drosophila and PP6 in vertebrates. Sit4 promotes transcription of G(1) cyclins and a sit4(ts) strain exhibits a G1 arrest at the restrictive temperature. The yeast sit4ts was rescued by expression of PPV or a chimeric phosphatase containing the first fifty-three residues of PPV fused to Drosophila PP1. The results suggested that the N terminus of the Sit4/PPV protein exerts a specific function in the yeast cell cycle. Here we tested whether the N terminus of human PP6 exerts specific effects on G(1)-S progression in human cells. The N terminus of PP6 or PP2A was fused to GFP and the proteins transiently expressed in prostate cancer PC-3 cells. Expression of the PP6 fusion protein was restricted to lower levels than either the PP2A fusion protein or GFP. However, the PP6 fusion protein blocked entry into S phase and increased by > 20% the proportion of cells in G1 phase. Expression of the PP6 fusion protein did not significantly change the levels of transcripts for cyclins or ca. eighty other cell cycle genes, but did suppress the levels of cyclin D1 protein in cells in G1 phase and reduce the phosphorylation of RB1 at Ser807/811. Thus, our results provide evidence that PP6 regulates cell cycle progression in human cells at least in part through control of cyclin D1 and the function of PP6 is distinct from its homolog Sit4 in yeast.