Maroto F G, Sierra J M
Centro de Biologia Molecular, Consejo Superior de Investigaciones Cientificas, Madrid, Spain.
J Biol Chem. 1988 Oct 25;263(30):15720-5.
Lysates from normally growing (25 degrees C) or heat shocked (37 degrees C, 45 min) Drosophila melanogaster embryos were obtained and the effect of analogues of the mRNA 5'-terminal cap, m7G(5')ppp(5')N structure and of potassium ions on their endogenous protein synthesis activity was studied. At optimal concentration of KCH3COO (75-80 mM), protein synthesis in normal lysates is strongly inhibited by cap analogues (m7GpppG, m7GDP, and m7GMP). At the same ionic conditions, heat shock lysates translate preferentially the heat shock messengers, and this translation is almost unaffected by the cap analogues. In contrast, residual synthesis of normal proteins in heat shock lysates was reduced by these compounds. By lowering the concentration of potassium ions it was possible to gradually reverse the inhibitory effect of the cap analogues in normal lysates and also to increase specifically the translation of normal mRNAs in heat shock lysates. Translation of normal mRNAs is also partial but specifically rescued by supplementing heat shock lysates with polypeptide chain initiation factors partially purified from rabbit reticulocytes. These data are consistent with the notion that the failure of normal mRNAs to be translated under heat shock conditions might be due, at least to some extent, to the inactivation of polypeptide chain initiation factor(s) involved in the recognition of the mRNA 5'-terminal cap structure.
获取正常生长（25摄氏度）或热激处理（37摄氏度，45分钟）的黑腹果蝇胚胎的裂解物，并研究mRNA 5'-末端帽类似物、m7G(5')ppp(5')N结构类似物以及钾离子对其内源性蛋白质合成活性的影响。在最佳醋酸钾浓度（75 - 80 mM）下，正常裂解物中的蛋白质合成受到帽类似物（m7GpppG、m7GDP和m7GMP）的强烈抑制。在相同离子条件下，热激裂解物优先翻译热激信使RNA，并且这种翻译几乎不受帽类似物的影响。相反，这些化合物降低了热激裂解物中正常蛋白质的残留合成。通过降低钾离子浓度，可以逐渐逆转帽类似物在正常裂解物中的抑制作用，还能特异性增加热激裂解物中正常mRNA的翻译。通过用从兔网织红细胞中部分纯化的多肽链起始因子补充热激裂解物，正常mRNA的翻译也能部分但特异性地得到挽救。这些数据与以下观点一致，即在热激条件下正常mRNA无法翻译，至少在一定程度上可能是由于参与识别mRNA 5'-末端帽结构的多肽链起始因子失活所致。
