Silencing of RNA helicase II/Gualpha inhibits mammalian ribosomal RNA production.
Silencing of RNA helicase II/Gualpha inhibits mammalian ribosomal RNA production.
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发表时间：
2003
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通讯作者：
D. Henning;Rolando B. So;Runyan Jin;L. Lau;B. Valdez
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作者：
D. Henning;Rolando B. So;Runyan Jin;L. Lau;B. Valdez
酵母中核糖体 RNA 的复杂生产过程已被明确定义，但其在高等生物体中的复杂性却鲜为人知。我们最近表明，非洲爪蟾卵母细胞中核仁蛋白 RNA 解旋酶 II/Gualpha（RH-II/Gualpha 或 DDX21）的下调抑制了 20 S rRNA 加工为 18 S，并导致 28 S rRNA 降解（Yang, H.、Zhou, J.、Ochs, R. L.、Henning, D.、Jin, R. 和 Valdez, B. C. (2003)化学杂志，278，38847-38859）。由于哺乳动物细胞中尚未对核仁 RNA 解旋酶进行功能表征，因此我们使用短干扰 RNA 来寻找 RH-II/Gualpha 及其旁系同源物 RH-II/Gubeta 在 rRNA 生产中的功能。在 HeLa 细胞中 RH-II/Gualpha 沉默超过 80%，导致 18 和 28 S rRNA 产生几乎被抑制 80%。这种抑制可以通过野生型 RH-II/Gualpha 的外源表达来逆转。具有 ATP 酶活性的解旋酶缺陷型突变体能够挽救 28 S rRNA 的产生，但不能挽救 18 S rRNA。当旁系同源物 RH-II/Gubeta 过表达时，还观察到表现出 18 S 和 28 S rRNA 产生抑制的表型。 RH-II/Gualpha 的下调和 RH-II/Gubeta 的过度表达均会减慢细胞增殖。两个旁系同源物的相反作用表明了拮抗功能。
The intricate production of ribosomal RNA is well defined in yeast, but its complexity in higher organisms is barely understood. We recently showed that down-regulation of nucleolar protein RNA helicase II/Gualpha (RH-II/Gualpha or DDX21) in Xenopus oocytes inhibited processing of 20 S rRNA to 18 S and contributed to degradation of 28 S rRNA (Yang, H., Zhou, J., Ochs, R. L., Henning, D., Jin, R., and Valdez, B. C. (2003) J. Biol. Chem. 278, 38847-38859). Since no nucleolar RNA helicase has been functionally characterized in mammalian cells, we used short interfering RNA to search for functions for RH-II/Gualpha and its paralogue RH-II/Gubeta in rRNA production. Silencing of RH-II/Gualpha by more than 80% in HeLa cells resulted in an almost 80% inhibition of 18 and 28 S rRNA production. This inhibition could be reversed by exogenous expression of wild type RH-II/Gualpha. A helicase-deficient mutant form having ATPase activity was able to rescue the production of 28 S but not 18 S rRNA. A phenotype exhibiting inhibition of 18 S and 28 S rRNA production was also observed when the paralogue RH-II/Gubeta was overexpressed. Both down-regulation of RH-II/Gualpha and overexpression of RH-II/Gubeta slowed cell proliferation. The opposite effects of the two paralogues suggest antagonistic functions.