THE TRANSLATIONAL REPRESSION MEDIATED BY THE PLATELET-DERIVED GROWTH-FACTOR 2/C-SIS MESSENGER-RNA LEADER IS RELIEVED DURING MEGAKARYOCYTIC DIFFERENTIATION
THE TRANSLATIONAL REPRESSION MEDIATED BY THE PLATELET-DERIVED GROWTH-FACTOR 2/C-SIS MESSENGER-RNA LEADER IS RELIEVED DURING MEGAKARYOCYTIC DIFFERENTIATION
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DOI：
10.1074/jbc.270.18.10559
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发表时间：
1995-05-05
影响因子：
4.8
通讯作者：
ELROYSTEIN, O
中科院分区：
文献类型：
--
作者：
BERNSTEIN, J;SHEFLER, I;ELROYSTEIN, O
血小板衍生生长因子2/c-sis基因的表达受到高度限制，并在多个水平上受到控制。其结构化的mRNA前导序列非常长（1022个核苷酸），是一种有效的翻译抑制剂。PDGF 2合成的位点之一是巨核细胞，这意味着在巨核细胞分化期间调节PDGF 2翻译效率。为了研究mRNA前导序列作为翻译顺式调节剂的作用，使用混合T7/牛痘胞质表达系统将控制转录、选择性剪接和mRNA稳定性的决定簇与控制翻译的决定簇断开。嵌合转录物，其中的人PDGF 2/c-sis mRNA前导序列位于报告基因的框架上游，用于确定是否mRNA前导序列可以赋予可变的翻译效率在分化过程中。结果表明，在K562细胞向巨核细胞分化的过程中，存在一个时间窗，在此时间窗内，PDGF 2/c-sis mRNA前导序列对K562细胞翻译的强烈抑制被解除。翻译抑制缓解的时间过程与分化过程中PDGF 2/c-sis转录诱导的时间过程相似。紧邻起始AUG密码子上游的179个核苷酸的富含CG的片段对于抑制翻译效率的严格调节是必需的。在翻译起始因子eIF 4 E过表达的NIH 3 T3中，c-sis的mRNA前导序列的抑制作用没有减轻，这表明巨核细胞分化过程中翻译机制的变化超出了eIF 4 E活性。一个5 '端独立的翻译机制的可能参与进行了讨论。
Expression of the platelet-derived growth factor 2/c-sis gene is highly restricted and controlled at multiple levels. Its structured mRNA leader, which is unusually long (1022 nucleotides), serves as a potent translational inhibitor. One of the sites of PDGF2 synthesis is megakaryocytes, implying that PDGF2 translation efficiency is modulated during megakaryocytic differentiation. To study the role of the mRNA leader as a translational cis-modulator, the hybrid T7/vaccinia cytoplasmic expression system was used to disconnect between determinants controlling transcription, alternative splicing, and mRNA stability from those controlling translation. Chimeric transcripts in which the human PDGF2/c-sis mRNA leader positioned in frame upstream of a reporter gene were used to determine whether the mRNA leader can confer variable translational efficiencies during differentiation. It is demonstrated that there is a time window during megakaryocytic differentiation of K562 cells in which the strong translational inhibition by PDGF2/c-sis mRNA leader is relieved. The time course of the translational repression relief is similar to that of PDGF2/c-sis transcriptional induction during the differentiation process. A 179-nucleotides CG-rich fragment immediately upstream of the initiator AUG codon is necessary for coffering stringent modulation of the translational efficiency. In NIH3T3 overexpressing translation initiation factor eIF4E, the inhibitory effect of the mRNA leader of c-sis is not relieved, suggesting that the changes in the translational machinery during megakaryocytic differentiation are beyond eIF4E activity. The possible involvement of a 5'-end independent translational mechanism is discussed.