GCN4 mRNA翻译控制中再起始调控的证据。
Evidence for regulation of reinitiation in translational control of GCN4 mRNA.
作者信息
Hinnebusch A G, Jackson B M, Mueller P P
机构信息
Unit of Molecular Genetics of Lower Eukaryotes, National Institute of Child Health and Human Development, Bethesda, MD 20892.
出版信息
Proc Natl Acad Sci U S A. 1988 Oct;85(19):7279-83. doi: 10.1073/pnas.85.19.7279.
Translational control of the GCN4 gene of Saccharomyces cerevisiae is mediated by four upstream open reading frames (URFs) present in the leader of GCN4 mRNA. URFs 3 and 4 efficiently repress GCN4 expression in normal growth conditions; URFs 1 and 2 are required to overcome this repression in amino acid-starved cells. lacZ fusions to URFs 3 and 4 were used to determine the translational event that is regulated at these sequences by URFs 1 and 2. URF3-lacZ, URF4-lacZ, and GCN4-lacZ fusions are affected similarly by URFs 1 and 2 when no other URFs are present in the leader: expression from all three fusions is reduced by an amount slightly greater in repressing than in derepressing conditions. These results are inconsistent with models that postulate a differential effect of URFs 1 and 2 on initiation or elongation rates at URFs 3 and 4 versus the GCN4 coding sequences. We propose that the efficiency of reinitiation at the GCN4 AUG codon after translation of URFs 3 and 4 is the translational event that is stimulated in derepressing conditions by URFs 1 and 2.
酿酒酵母GCN4基因的翻译调控由GCN4 mRNA前导区中的四个上游开放阅读框（URF）介导。在正常生长条件下，URF3和URF4可有效抑制GCN4的表达；在氨基酸饥饿的细胞中，需要URF1和URF2来克服这种抑制作用。利用与URF3和URF4的lacZ融合体来确定在这些序列上受URF1和URF2调控的翻译事件。当在前导区不存在其他URF时，URF3-lacZ、URF4-lacZ和GCN4-lacZ融合体受URF1和URF2的影响类似：在抑制条件下，所有这三种融合体的表达降低幅度略大于去抑制条件下的降低幅度。这些结果与假设URF1和URF2对URF3和URF4与GCN4编码序列的起始或延伸速率有不同影响的模型不一致。我们提出，在翻译URF3和URF4后，GCN4 AUG密码子处重新起始的效率是在去抑制条件下受URF1和URF2刺激的翻译事件。
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