title: The two tempos of nuclear pore complex evolution: highly adapting proteins in an ancient frozen structure.
abstract: BACKGROUND
  The origin of the nuclear compartment has been extensively debated, leading to several alternative views on the evolution of the eukaryotic nucleus. Until recently, too little phylogenetic information was available to address this issue by using multiple characters for many lineages.
  
  
  RESULTS
  We analyzed 65 proteins integral to or associated with the nuclear pore complex (NPC), including all the identified nucleoporins, the components of their anchoring system and some of their main partners. We used reconstruction of ancestral sequences of these proteins to expand the detection of homologs, and showed that the majority of them, present all over the nuclear pore structure, share homologs in all extant eukaryotic lineages. The anchoring system, by contrast, is analogous between the different eukaryotic lineages and is thus a relatively recent innovation. We also showed the existence of high heterogeneity of evolutionary rates between these proteins, as well as between and within lineages. We show that the ubiquitous genes of the nuclear pore structure are not strongly conserved at the sequence level, and that only their domains are relatively well preserved.
  
  
  CONCLUSIONS
  We propose that an NPC very similar to the extant one was already present in at least the last common ancestor of all extant eukaryotes and it would not have undergone major changes since its early origin. Importantly, we observe that sequences and structures obey two very different tempos of evolution. We suggest that, despite strong constraints that froze the structural evolution of the nuclear pore, the NPC is still highly adaptive, modern, and flexible at the sequence level.
authors.affiliation: Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 1X5, Canada. Eric.Bapteste@Dal.ca
authors.forename: Eric
authors.initials: E
authors.lastname: Bapteste
authors.forename: Robert L
authors.initials: RL
authors.lastname: Charlebois
authors.forename: Dave
authors.initials: D
authors.lastname: MacLeod
authors.forename: Céline
authors.initials: C
authors.lastname: Brochier
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D003080:Cold Temperature; D005057:Eukaryotic Cells / Q000737:chemistry; D019143:Evolution, Molecular; D005615:Freezing; D022022:Nuclear Pore / Q000737:chemistry*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D011387:Prokaryotic Cells / Q000737:chemistry; D017434:Protein Structure, Tertiary; D013997:Time Factors
chemical_list: D028861:Nuclear Pore Complex Proteins