Coordinated nuclear export of 60S ribosomal subunits and NMD3 in vertebrates
Coordinated nuclear export of 60S ribosomal subunits and NMD3 in vertebrates
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DOI：
10.1093/emboj/cdg249
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发表时间：
2003-06-02
期刊：
影响因子：
11.4
通讯作者：
Dahlberg, JE
中科院分区：
文献类型：
--
作者：
Trotta, CR;Lund, E;Dahlberg, JE
60 S和40 S核糖体亚基在核仁中组装，并彼此独立地从细胞核输出到细胞质。我们发现，在脊椎动物细胞中，这两个亚基的运输需要出口受体CRM 1和Ran. GTP。60 S亚基的输出与核质穿梭蛋白NMD 3的输出偶联。人NMD 3（hNMD 3）含有CRM-1依赖的富含亮氨酸的核输出信号（内斯）和复杂的分散的核定位信号（NLS），其碱性区域也是核仁积累所需的。当存在于非洲爪蟾卵母细胞中时，野生型和出口缺陷型突变hNMD 3蛋白在亚基成熟的后期结合到新制造的核60 S前出口颗粒。输出缺陷型hNMD 3，而不是野生型蛋白，抑制出口的60 S亚基从卵母细胞核。这些结果表明，内斯突变蛋白与内源性野生型蛙NMD 3竞争结合新生60 S亚基，从而阻止它们的输出。我们提出NMD 3作为CRM 1-Ran. GTP介导的60 S亚基输出的适配器，通过从脊椎动物到酵母的保守机制。
60S and 40S ribosomal subunits are assembled in the nucleolus and exported from the nucleus to the cytoplasm independently of each other. We show that in vertebrate cells, transport of both subunits requires the export receptor CRM1 and Ran.GTP. Export of 60S subunits is coupled with that of the nucleo- cytoplasmic shuttling protein NMD3. Human NMD3 (hNMD3) contains a CRM-1-dependent leucine-rich nuclear export signal (NES) and a complex, dispersed nuclear localization signal (NLS), the basic region of which is also required for nucleolar accumulation. When present in Xenopus oocytes, both wild-type and export-defective mutant hNMD3 proteins bind to newly made nuclear 60S pre-export particles at a late step of subunit maturation. The export-defective hNMD3, but not the wild-type protein, inhibits export of 60S subunits from oocyte nuclei. These results indicate that the NES mutant protein competes with endogenous wild-type frog NMD3 for binding to nascent 60S subunits, thereby preventing their export. We propose that NMD3 acts as an adaptor for CRM1-Ran.GTP-mediated 60S subunit export, by a mechanism that is conserved from vertebrates to yeast.