Glutamic acid mutagenesis of retinoblastoma protein phosphorylation sites has diverse effects on function
Glutamic acid mutagenesis of retinoblastoma protein phosphorylation sites has diverse effects on function
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DOI：
10.1038/sj.onc.1203332
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发表时间：
2000-01-27
期刊：
影响因子：
8
通讯作者：
Goodrich, DW
中科院分区：
文献类型：
--
作者：
Barrientes, S;Cooke, C;Goodrich, DW
视网膜母细胞瘤肿瘤抑制基因（Rb）在细胞内具有多种功能，包括调控转录、分化、凋亡和细胞周期。这些功能的调节是由体内多达16个细胞周期蛋白依赖性激酶（CDK）磷酸化位点的磷酸化介导的。这些位点对各种Rb功能调控的贡献尚不清楚。为了表征这些位点磷酸化的影响，我们系统地将丝氨酸或苏氨酸诱变为谷氨酸。研究人员分析了35个具有不同磷酸化修饰位点组合的突变体对细胞周期的阻滞能力和诱导分化的潜力。只有高度取代的突变体不能阻止细胞周期进程，然而，只有四个修饰磷酸化位点的突变体不能促进分化。其他突变体在该试验中活性增加。我们得出结论，Rb磷酸化位点的修饰可以增加或降低蛋白质活性，不同的Rb功能可以通过不同位点的组合独立调节，并且任何一个位点的修饰效果都依赖于上下文。
The retinoblastoma tumor suppressor gene (Rb) has many functions within the cell including regulation of transcription, differentiation, apoptosis, and the cell cycle. Regulation of these functions is mediated by phosphorylation at as many as 16 cyclin-dependent kinase (CDK) phosphorylation sites in vivo. The contribution of these sites to the regulation of the various Rb functions is not well understood. To characterize the effect of phosphorylation at these sites, we systematically mutagenized the serines or threonines to glutamic acid. Thirty-five mutants with different combinations of modified phosphorylation sites were assayed for their ability to arrest the cell cycle and for their potential to induce differentiation. Only the most highly substituted mutants failed to arrest cell cycle progression, However, mutants with as few as four modified phosphorylation sites were unable to promote differentiation. Other mutants had increased activity in this assay. We conclude that modification of Rb phosphorylation sites can increase or decrease protein activity, that different Rb functions can be regulated independently by distinct combinations of sites, and that the effects of modification at any one site are context dependent.