scholarly journals Evidence supporting a viral origin of the eukaryotic nucleus

2019 ◽  
Author(s):  
Philip JL Bell
Keyword(s):  
Nuclear Export ◽  
Common Ancestor ◽  
Eukaryotic Cell ◽  
Viral Origin ◽  
Eukaryotic Nucleus ◽  
Complex Process ◽  
Bona Fide ◽  
Viral Factory ◽  
Acting In Concert ◽  
Archaeal Ancestor

AbstractThe defining feature of the eukaryotic cell is the possession of a nucleus that uncouples transcription from translation. This uncoupling of transcription from translation depends on a complex process employing hundreds of eukaryotic specific genes acting in concert and requires the 7-methylguanylate (m7G) cap to prime eukaryotic mRNA for splicing, nuclear export, and cytoplasmic translation. The origin of this complex system is currently a paradox since it is not found or needed in prokaryotic cells which lack nuclei, yet it was apparently present and fully functional in the Last Eukaryotic Common Ancestor (LECA). According to the Viral Eukaryogenesis (VE) hypothesis the abrupt appearance of the nucleus in the eukaryotic lineage occurred because the nucleus descends from the viral factory of a DNA phage that infected the archaeal ancestor of the eukaryotes. Consequently, the system for uncoupling of transcription from translation in eukaryotes is predicted by the VE hypothesis to be viral in origin. In support of this hypothesis it is shown here that m7G capping apparatus that primes the uncoupling of transcription from translation in eukaryotes is present in viruses of the Mimiviridae but absent from bona-fide archaeal relatives of the eukaryotes such as Lokiarchaeota. Furthermore, phylogenetic analysis of the m7G capping pathway indicates that eukaryotic nuclei and Mimiviridae obtained this pathway from a common ancestral source that predated the origin of LECA. These results support the VE hypothesis and suggest the eukaryotic nucleus and the Mimiviridae descend from a common First Eukaryotic Nuclear Ancestor (FENA).

The comparative biochemistry of viruses and humans: an evolutionary path towards autoimmunity

2019 ◽  
Vol 400 (5) ◽  
pp. 629-638 ◽  
Author(s):  
Darja Kanduc
Keyword(s):  
Measles Virus ◽  
Influenza A ◽  
Viral Infections ◽  
Sequence Similarity ◽  
Eukaryotic Cell ◽  
Point Of View ◽  
Peptide Sequence ◽  
Human Viruses ◽  
Archaeal Ancestor ◽  
Borna Disease

Abstract Analyses of the peptide sharing between five common human viruses (Borna disease virus, influenza A virus, measles virus, mumps virus and rubella virus) and the human proteome highlight a massive viral vs. human peptide overlap that is mathematically unexpected. Evolutionarily, the data underscore a strict relationship between viruses and the origin of eukaryotic cells. Indeed, according to the viral eukaryogenesis hypothesis and in light of the endosymbiotic theory, the first eukaryotic cell (our lineage) originated as a consortium consisting of an archaeal ancestor of the eukaryotic cytoplasm, a bacterial ancestor of the mitochondria and a viral ancestor of the nucleus. From a pathologic point of view, the peptide sequence similarity between viruses and humans may provide a molecular platform for autoimmune crossreactions during immune responses following viral infections/immunizations.

scholarly journals Structural characterization of a Thorarchaeota profilin indicates eukaryotic-like features but with an extended N-terminus

2021 ◽  
Author(s):  
Celestine N Chi ◽  
Ravi Teja Inturi ◽  
Sandra Martinez Lara ◽  
Mahmoud Darweesh
Keyword(s):  
Common Ancestor ◽  
Three Dimensional ◽  
Eukaryotic Cell ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Last Eukaryotic Common Ancestor ◽  
Rigid Core ◽  
N Terminus ◽  
Metagenomics Analysis

The emergence of the first eukaryotic cell was preceded by evolutionary events which are still highly debatable. Recently, comprehensive metagenomics analysis has uncovered that the Asgard super-phylum is the closest yet known archaea host of eukaryotes. However, it remains to be established if a large number of eukaryotic signature proteins predicated to be encoded by the Asgard super-phylum are functional at least, in the context of a eukaryotic cell. Here, we determined the three-dimensional structure of profilin from Thorarchaeota by nuclear magnetic resonance spectroscopy and show that this profilin has a rigid core with a flexible N-terminus which was previously implicated in polyproline binding. In addition, we also show that thorProfilin co-localizes with eukaryotic actin in cultured HeLa cells. This finding reaffirm the notion that Asgardean encoded proteins possess eukaryotic-like characteristics and strengthen likely existence of a complex cytoskeleton already in a last eukaryotic common ancestor

scholarly journals Interaction of mammalian neprilysin with binding protein and calnexin in Schizosaccharomyces pombe

1999 ◽  
Vol 340 (3) ◽  
pp. 813-819 ◽  
Author(s):  
Hugues BEAULIEU ◽  
Aram ELAGÖZ ◽  
Philippe CRINE ◽  
Luis A. ROKEACH
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Binding Protein ◽  
Cell Types ◽  
Neutral Endopeptidase ◽  
Integral Membrane Protein ◽  
Eukaryotic Cell ◽  
Unfolded Proteins ◽  
Folding Intermediates ◽  
Bona Fide ◽  
The Brain

Neutral endopeptidase (neprilysin or NEP, EC 3.4.24.11) is a zinc metallo-endopeptidase expressed in many eukaryotic cell types and displaying several important physiological roles. In the brain (and central nervous system), this enzyme is involved in the molecular mechanism of pain by its action in the degradation of enkephalin molecules. In the kidney, NEP is implicated in the degradation of regulatory factors involved in the control of arterial pressure, including atrial natriuretic peptide and bradykinin. In this study we assessed the potential of the fission yeast Schizosaccharomyces pombe to overproduce rabbit NEP and secreted NEP (sNEP, a soluble derivative of this integral membrane protein). Both recombinant NEP and sNEP were produced at high levels (5 mg/l) in this system. Enzymic studies revealed that these recombinant proteins were fully active and exhibit kinetic parameters similar to those of the bona fide enzyme. Immunofluorescence microscopy and enzymic assays demonstrated that recombinant NEP is correctly targeted to the cell membrane. Furthermore, co-immunoprecipitation studies showed that folding intermediates of NEP and sNEP, produced in S. pombe, interact in the endoplasmic reticulum (ER) with binding protein (BiP) and calnexin (Cnx1p). The amount of sNEP coprecipitated with both BiP and Cnx1p augmented when cells were subjected to various stresses causing the accumulation of unfolded proteins in the ER. The interactions of NEP with BiP and Cnx1p were, however, more refractive to the same stresses.

scholarly journals Molecular convergence by differential domain acquisition is a hallmark of chromosomal passenger complex evolution

2022 ◽  
Author(s):  
Shinichiro Komaki ◽  
Eelco C Tromer ◽  
Geert De Jaeger ◽  
Nancy De Winne ◽  
Maren Heese ◽  
...  
Keyword(s):  
Common Ancestor ◽  
Eukaryotic Cell ◽  
Binding Domain ◽  
Phosphate Binding ◽  
Fha Domain ◽  
Developmental Defects ◽  
Chromosomal Passenger Complex ◽  
Chromosomal Passenger ◽  
Similarity Searches ◽  
Bir Domain

The chromosomal passenger complex (CPC) is a heterotetrameric regulator of eukaryotic cell division, consisting of an Aurora-type kinase and a scaffold built of INCENP, Borealin and Survivin. While most CPC components are conserved across eukaryotes, orthologs of the chromatin reader Survivin have previously only been found in animals and fungi, raising the question of how its essential role is carried out in other eukaryotes. By characterizing proteins that bind to the Arabidopsis Borealin ortholog, we identified BOREALIN RELATED INTERACTOR 1 and 2 (BORI1 and BORI2) as redundant Survivin-like proteins in the context of the CPC in plants. Loss of BORI function is lethal and a reduced expression of BORIs causes severe developmental defects. Similar to Survivin, we find that the BORIs bind to phosphorylated histone H3, relevant for correct CPC association with chromatin. However, this interaction is not mediated by a BIR domain as in previously recognized Survivin orthologs, but by an FHA domain, a widely conserved phosphate-binding module. We propose that the unifying criterion of Survivin-type proteins is a helix that facilitates complex formation with the other two scaffold components, and that the addition of a phosphate-binding domain, necessary for concentration at the inner centromere, evolved in parallel in different eukaryotic groups. Using sensitive similarity searches, we indeed find conservation of this helical domain between animals and plants, and identify the missing CPC component in most eukaryotic supergroups. Interestingly, we also detect Survivin orthologs without a defined phosphate-binding domain, possibly reflecting the situation in the last eukaryotic common ancestor.

scholarly journals Arp2/3 complex-mediated actin assembly drives microtubule-independent motility and phagocytosis in the evolutionarily divergent amoeba Naegleria

2020 ◽  
Author(s):  
Katrina B. Velle ◽  
Lillian K. Fritz-Laylin
Keyword(s):  
Actin Cytoskeleton ◽  
Common Ancestor ◽  
Genomic Analysis ◽  
Eukaryotic Cell ◽  
Model System ◽  
Human Cells ◽  
Actin Assembly ◽  
Cell Type ◽  
Cytoplasmic Microtubules ◽  
Work Supports

ABSTRACTMuch of our current understanding of actin-driven phenotypes in eukaryotes has come from the “yeast to human” opisthokont lineage, as well as the related amoebozoa. Outside of these groups lies the genus Naegleria, which shared a common ancestor with humans over a billion years ago, and includes the deadly “brain-eating amoeba.” Unlike nearly every other known eukaryotic cell type, Naegleria amoebae are thought to lack cytoplasmic microtubules. The absence of microtubules suggests that these amoebae rapidly crawl and phagocytose bacteria using actin alone. Although this makes Naegleria a powerful system to probe actin-driven functions in the absence of microtubules, surprisingly little is known about Naegleria’s actin cytoskeleton. Here, we use microscopy and genomic analysis to show that Naegleria amoebae have an extensive actin cytoskeletal repertoire, complete with nucleators and nucleation promoting factors. Naegleria use this cytoskeletal machinery to generate Arp2/3-dependent lamellar protrusions, which correlate with the capacity to migrate and phagocytose bacteria. Because human cells also use Arp2/3-dependent lamellar protrusions for motility and phagocytosis, this work supports an evolutionarily ancient origin for these actin-driven processes and establishes Naegleria as a natural model system for studying microtubule-independent cytoskeletal phenotypes.

scholarly journals The Common Ancestor of Archaea and Eukarya Was Not an Archaeon

Archaea ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-18 ◽  
Author(s):  
Patrick Forterre
Keyword(s):  
Common Ancestor ◽  
Phylogenetic Analyses ◽  
Critical Role ◽  
Last Common Ancestor ◽  
Dna Viruses ◽  
The Common ◽  
Basic Features ◽  
Origin Of Eukaryotes ◽  
Archaeal Ancestor ◽  
Selection Of

It is often assumed that eukarya originated from archaea. This view has been recently supported by phylogenetic analyses in which eukarya are nested within archaea. Here, I argue that these analyses are not reliable, and I critically discuss archaeal ancestor scenarios, as well as fusion scenarios for the origin of eukaryotes. Based on recognized evolutionary trends toward reduction in archaea and toward complexity in eukarya, I suggest that their last common ancestor was more complex than modern archaea but simpler than modern eukaryotes (the bug in-between scenario). I propose that the ancestors of archaea (and bacteria) escaped protoeukaryotic predators by invading high temperature biotopes, triggering their reductive evolution toward the “prokaryotic” phenotype (the thermoreduction hypothesis). Intriguingly, whereas archaea and eukarya share many basic features at the molecular level, the archaeal mobilome resembles more the bacterial than the eukaryotic one. I suggest that selection of different parts of the ancestral virosphere at the onset of the three domains played a critical role in shaping their respective biology. Eukarya probably evolved toward complexity with the help of retroviruses and large DNA viruses, whereas similar selection pressure (thermoreduction) could explain why the archaeal and bacterial mobilomes somehow resemble each other.

scholarly journals The role of mitochondrial energetics in the origin and diversification of eukaryotes

2021 ◽  
Author(s):  
Paul E Schavemaker ◽  
Sergio A Munoz-Gomez
Keyword(s):  
Cell Surface ◽  
Surface Area ◽  
Energy Demand ◽  
Common Ancestor ◽  
Eukaryotic Cell ◽  
Cell Surfaces ◽  
Energy Excess ◽  
Potential Factors ◽  
Cell Volumes

The origin of eukaryotic cell size and complexity is thought by some to have required an energy excess provided by mitochondria, whereas others claim that mitochondria provide no energetic boost to eukaryotes. Recent observations show that energy demand scales continuously and linearly with cell volume across both prokaryotes and eukaryotes, and thus suggest that eukaryotes do not have an increased energetic capacity over prokaryotes. However, amounts of respiratory membranes and ATP synthases scale super-linearly with cell surface area. Furthermore, the energetic consequences of the contrasting genomic designs between prokaryotes and eukaryotes have yet to be precisely quantified. Here, we investigated (1) potential factors that affect the cell volumes at which prokaryotes become surface area-constrained, and (2) the amount of energy that is divested to increasing amounts of DNA due to the contrasting genomic designs of prokaryotes and eukaryotes. Our analyses suggest that prokaryotes are not necessarily constrained by their cell surfaces at cell volumes of 100-103 µm3, and that the genomic design of eukaryotes is only slightly advantageous at genomes sizes of 106-107 bp. This suggests that eukaryotes may have first evolved without the need for mitochondria as these ranges hypothetically encompass the Last Eukaryote Common Ancestor and its proto-eukaryotic ancestors. However, our analyses also show that increasingly larger and fast-dividing prokaryotes would have a shortage of surface area devoted to respiration and would disproportionally divest more energy to DNA synthesis at larger genome sizes. We thus argue that, even though mitochondria may not have been required by the first eukaryotes, the successful diversification of eukaryotes into larger and more active cells was ultimately contingent upon the origin of mitochondria.

Origin of the eukaryotic nucleus: eukaryotes and eocytes are genotypically related

1989 ◽  
Vol 35 (1) ◽  
pp. 109-118 ◽  
Author(s):  
James A. Lake
Keyword(s):  
Common Ancestor ◽  
Sulfur Metabolism ◽  
Nuclear Genes ◽  
Rrna Genes ◽  
Last Common Ancestor ◽  
Nucleotide Substitutions ◽  
Eukaryotic Nucleus ◽  
Eukaryotic Group

The origin of the eukaryotic nucleus is difficult to reconstruct. While eukaryotic organelles (chloroplast, mitochondrion) are eubacterial endosymbionts, the source of nuclear genes has been obscured by multiple nucleotide substitutions. Using evolutionary parsimony, a newly developed rate-invariant treeing algorithm, the eukaryotic rRNA genes are shown to have evolved from the eocytes, a group of extremely thermophilic, sulfur-metabolizing, anucleate cells. The deepest bifurcation yet found separates the reconstructed tree into two taxonomic divisions. These are a proto-eukaryotic group (karyotes) and an essentially bacterial one (parkaryotes). Within the precision of the rooting procedure, the tree is not consistent with either the prokaryotic–eukaryotic or the archaebacterial–eubacterial–eukaryotic groupings. It implies that the last common ancestor of extant life, and the early ancestors of eukaryotes, very likely lacked nuclei, metabolized sulfur, and lived at near boiling temperatures.Key words: rRNA, evolution, phylogeny, sulfur metabolism.

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