Department of Molecular Biology and Functional Genomics, Stockholm University, Stockholm, Sweden.
PLoS One. 2010 Oct 8;5(10):e13241. doi: 10.1371/journal.pone.0013241.
The Nuclear Pore Complex (NPC) facilitates molecular trafficking between nucleus and cytoplasm and is an integral feature of the eukaryote cell. It exhibits eight-fold rotational symmetry and is comprised of approximately 30 nucleoporins (Nups) in different stoichiometries. Nups are broadly conserved between yeast, vertebrates and plants, but few have been identified among other major eukaryotic groups.
METHODOLOGY/PRINCIPAL FINDINGS: We screened for Nups across 60 eukaryote genomes and report that 19 Nups (spanning all major protein subcomplexes) are found in all eukaryote supergroups represented in our study (Opisthokonts, Amoebozoa, Viridiplantae, Chromalveolates and Excavates). Based on parsimony, between 23 and 26 of 31 Nups can be placed in LECA. Notably, they include central components of the anchoring system (Ndc1 and Gp210) indicating that the anchoring system did not evolve by convergence, as has previously been suggested. These results significantly extend earlier results and, importantly, unambiguously place a fully-fledged NPC in LECA. We also test the proposal that transmembrane Pom proteins in vertebrates and yeasts may account for their variant forms of mitosis (open mitoses in vertebrates, closed among yeasts). The distribution of homologues of vertebrate Pom121 and yeast Pom152 is not consistent with this suggestion, but the distribution of fungal Pom34 fits a scenario wherein it was integral to the evolution of closed mitosis in ascomycetes. We also report an updated screen for vesicle coating complexes, which share a common evolutionary origin with Nups, and can be traced back to LECA. Surprisingly, we find only three supergroup-level differences (one gain and two losses) between the constituents of COPI, COPII and Clathrin complexes.
CONCLUSIONS/SIGNIFICANCE: Our results indicate that all major protein subcomplexes in the Nuclear Pore Complex are traceable to the Last Eukaryotic Common Ancestor (LECA). In contrast to previous screens, we demonstrate that our conclusions hold regardless of the position of the root of the eukaryote tree.
核孔复合物（NPC）促进核质之间的分子运输，是真核细胞的一个基本特征。它具有八重旋转对称性，由不同比例的约 30 个核孔蛋白（Nups）组成。Nups 在酵母、脊椎动物和植物之间广泛保守，但在其他主要真核生物群中很少被发现。
方法/主要发现：我们在 60 个真核生物基因组中筛选 Nups，并报告在我们研究中代表的所有真核生物超群（后生动物、变形虫、绿色植物、色素体和挖掘虫）中都发现了 19 个 Nups（跨越所有主要蛋白质亚复合物）。基于简约性，可以将 31 个 Nups 中的 23 到 26 个放置在 LECA 中。值得注意的是，它们包括锚定系统的中心组件（Ndc1 和 Gp210），表明锚定系统不是像以前那样通过趋同进化而来的。这些结果大大扩展了早期的结果，并且重要的是，明确地将一个成熟的 NPC 放置在 LECA 中。我们还测试了一个假设，即脊椎动物和酵母中的跨膜 Pom 蛋白可能解释了它们不同形式的有丝分裂（脊椎动物的开放有丝分裂，酵母的封闭有丝分裂）。脊椎动物 Pom121 和酵母 Pom152 的同源物的分布与该假设不一致，但真菌 Pom34 的分布符合这样一种情况，即在子囊菌的封闭有丝分裂进化中它是必不可少的。我们还报告了一个更新的囊泡涂层复合物的筛选，这些复合物与 Nups 具有共同的进化起源，可以追溯到 LECA。令人惊讶的是，我们在 COPI、COPII 和网格蛋白复合物的组成成分之间只发现了三个超级群水平的差异（一个获得和两个丢失）。
结论/意义：我们的结果表明，核孔复合物的所有主要蛋白质亚复合物都可以追溯到最后一个真核生物共同祖先（LECA）。与以前的筛选不同，我们证明我们的结论无论真核生物树的根的位置如何都成立。
