Accelerated mRNA decay in conditional mutants of yeast mRNA capping enzyme
Accelerated mRNA decay in conditional mutants of yeast mRNA capping enzyme
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DOI：
10.1093/nar/26.9.2050
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发表时间：
1998-05-01
影响因子：
14.9
通讯作者：
Shuman, S
中科院分区：
文献类型：
--
作者：
Schwer, B;Mao, XD;Shuman, S
目前酵母中mRNA衰变的模型表明，3 '去腺苷化先于5'帽的酶促去除，然后将裸端暴露于5 '核酸外切酶作用。在这里，我们分析了基因表达的酿酒酵母细胞轴承条件突变的Ceg1（加帽酶），一个52 kDa的蛋白质，转移GMP从GTP的5 '端的mRNA，形成GpppN帽结构。ceg1突变体的限制性温度的转变引起蛋白质合成速率的快速下降，这与多个个体mRNA的稳态水平的急剧下降相关。ceg1突变阻止了在限制性温度下新合成的SSA1和SSA4 mRNA的积累。未加帽的poly（A）（+）SSA4 mRNA在缺乏5 '核糖核酸外切酶Xrn1的细胞中积累。这些发现为长期持有的观点提供了遗传学证据，即帽状鸟苷酸对mRNA稳定性至关重要。当Ceg1失活时，去腺苷化-去帽-降解途径似乎短路。
Current models of mRNA decay in yeast posit that 3' deadenylation precedes enzymatic removal of the 5' cap, which then exposes the naked end to 5' exonuclease action. Here, we analyzed gene expression in Saccharomyces cerevisiae cells bearing conditional mutations of Ceg1 (capping enzyme), a 52 kDa protein that transfers GMP from GTP to the 5' end of mRNA to form the GpppN cap structure. Shift of ceg1 mutants to restrictive temperature elicited a rapid decline in the rate of protein synthesis, which correlated with a sharp reduction in the steady-state levels of multiple individual mRNAs. ceg1 mutations prevented the accumulation of SSA1 and SSA4 mRNAs that were newly synthesized at the restrictive temperature. Uncapped poly(A)(+) SSA4 mRNA accumulated in cells lacking the 5' exoribonuclease Xrn1. These findings provide genetic evidence for the long-held idea that the cap guanylate is critical for mRNA stability. The deadenylation-decapping-degradation pathway appears to be short-circuited when Ceg1 is inactivated.