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首页> 外文期刊>Nucleic acids research >Zinc ions are differentially required for the transcription of ribosomal 5S RNA and tRNA in a HeLa-cell extract
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Zinc ions are differentially required for the transcription of ribosomal 5S RNA and tRNA in a HeLa-cell extract

机译：锌离子在Hela细胞提取物中转录核糖体5S RNA和TRNA的转录所需的差异

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摘要

Chelation of divalent cations by 5 mM EDTA and subsequent removal by dialysis from a cytoplasmic HeLa cell extract leads to a complete loss of 5S rRNA transcription without affecting tRNA synthesis. Transcription complexes for 5S RNA can no longer be assembled in such a zinc-depleted extract and this ability can be fully restored only by the re-addition of 5 μM zinc. Reconstitution experiments with isolated protein fractions show that transcription factor A from HeLa-cells requires zinc to exert its specific function. Pre-formation of transcription complexes partially protects the metal ion against removal by chelation even in the presence of 1.8 M KC1. These results indicate that the zinc ions are bound to mammalian transcription factor IIIA which, in a transcription complex, binds very strongly to the 5S RNA gene. Cation depletion with 75 mM EDTA also suppresses tRNA transcription; an effect which is reversible by zinc addition. We conclude that beside for the binding of TF IIIA, zinc is also bound with a different affinity to a transcription component common to 5S and tRNA synthesis, most likely polymerase III itself.
机译：二价阳离子的螯合螯合5mm EDTA和随后由透析从细胞质Hela细胞提取物中除去的除去，导致5S rRNA转录的完全损失，而不会影响TRNA合成。 5S RNA的转录复合物不能再在这种锌耗尽的提取物中组装，并且这种能力只能通过再加入5μm锌来完全恢复。具有分离的蛋白质级分的重构实验表明，来自HeLa细胞的转录因子A需要锌施加其特定功能。转录复合物的预形成，即使在1.8M KCl的存在下，也可以通过螯合来部分保护金属离子通过螯合去除。这些结果表明，锌离子与哺乳动物转录因子IIIa结合，在转录复合物中，其与5S RNA基因非常强烈结合。 75 mm EDTA的阳离子耗竭也抑制了TRNA转录;一种通过锌添加的效果。我们得出结论，除了TF IIIa的结合之外，还与常见的转录组分不同的亲和力不同，锌也与5S和TRNA合成共同的转录组分，最可能的聚合酶III本身。

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