Determining the molecular mechanisms of ribosomal export through the nuclear pore.

我们研究计划的长期目标是研究不同生物体中必需RNA-蛋白质复合物的成熟途径。核糖体是细胞蛋白质生产机器，因此对每个细胞和生物体都至关重要。核糖体生物合成是一个复杂的过程，涉及200多种蛋白质。在细胞中，核糖体在核仁（细胞核的专门区室）内加工和组装，并且一旦成熟，它们就被输出到细胞质中以在翻译期间发挥作用。分子从细胞核转运到细胞质时要穿过核孔，核孔是一种嵌在核膜上的大分子复合物。特定的蛋白质，输出因子，是特定于不同的运输复合物，介导通过孔的运输。虽然已经确定了核糖体的转运因子，但对核糖体输出的实际机制知之甚少。特别是，仍不清楚像核糖体（直径约35 nm）这样大的大分子如何通过核篮的顶部（直径约25 nm）或辐条（直径约12.5 nm），核篮是控制进入运输通道的核孔的核结构，据信这对所有生物体中的所有核孔都是通用的。我们希望了解核糖体通过核孔复合物输出的分子机制，以及核篮的作用，以及特定核孔蛋白在核糖体靶向、易位和最终释放到细胞质中的功能。在面包酵母S.cerevisiae中，在邻近核仁的区域中已经鉴定出无篮孔。这表明这些无篮孔可能专门用于核糖体输出。然而，在人类细胞中尚未观察到无篮孔，这提出了进化保守的核糖体成熟途径的问题。由于它们的重要功能，核糖体在物种之间高度保守，即使是像古细菌和人类这样遥远的生物，它们成熟的大多数方面也是如此。然而，由于生物体的复杂性，以及功能失调的核糖体的潜在后果，如人类的恶性细胞增殖和疾病发展，可能存在显着差异。我们将确定核篮在核糖体输出中的作用以及无核篮孔的功能，这一点尚不清楚。此外，我们还将确定人类细胞中是否存在无篮孔，并研究低等和高等真核生物（即酵母和人类）之间核糖体输出的差异。

The long-term objective of our research program is to study the maturation pathways of essential RNA-protein complexes in different organisms. Ribosomes are the cellular protein production machinery and as such vital to every cell and organism. Ribosome biogenesis is a complex process that involves more than 200 proteins. In cells, ribosomes are processed and assembled within the nucleolus, a specialized compartment of the nucleus, and, once mature, they are exported to the cytoplasm to function during translation. Molecules transporting from the nucleus to the cytoplasm pass through the nuclear pore, a macromolecular complex embedded in the nuclear membrane. Specified proteins, export factors, that are particular to different transporting complexes, mediate transport through the pores. While transport factors have been identified for ribosomes, very little is known about the actual mechanisms of ribosome export. In particular, it is still unclear how a macromolecule as big as the ribosome (~35nm diameter) can pass through the top (~25nm diameter) or spokes (~12.5nm diameter) of the nuclear basket, a nuclear structure of the nuclear pore controlling access to the transport channel, which is believed to be universal to all nuclear pores in all organisms. We want to understand the molecular mechanisms of ribosome export through the nuclear pore complex, and the role of the nuclear basket as well as the function of specific nucleoporins during the targeting, translocation and finally release of ribosomes into the cytoplasm. In the baker’s yeast S.cerevisiae, basket-less pores have been identified in an area adjacent to the nucleolus. This suggests the possibility that these basket-less pores could be dedicated to ribosome export. However, basket-less pores have not yet been observed in human cells, which raises the question of how evolutionary conserved ribosome maturation pathways are. Due to their vital function, ribosomes are highly conserved between species, even organisms as distant as Archeabacteria and humans, and so are most aspects of their maturation. However, there may be significant differences due to the complexity of the organism, and the potential consequences of dysfunctional ribosomes, such as malignant cell proliferation and disease development in humans. We will establish the role of the nuclear basket in ribosome export and the function of basket-less nuclear pores, which is as yet unclear. Furthermore, we will determine the existence of basket-less pores in human cells, and examine the differences in ribosome export between lower and higher eukaryotes, namely yeast and humans.