Journal of Molecular Evolution

, Volume 52, Issue 5, pp 419–425 | Cite as

Poxviruses and the Origin of the Eukaryotic Nucleus

  • Masaharu  Takemura


A number of molecular forms of DNA polymerases have been reported to be involved in eukaryotic nuclear DNA replication, with contributions from α-, δ-, and ε-polymerases. It has been reported that δ-polymerase possessed a central role in DNA replication in archaea, whose ancestry are thought to be closely related to the ancestor of eukaryotes. Indeed, in vitro experiment shown here suggests that δ-polymerase has the potential ability to start DNA synthesis immediately after RNA primer synthesis. Therefore, the question arises, where did the α-polymerase come from? Phylogenetic analysis based on the nucleotide sequence of several conserved regions reveals that two poxviruses, vaccinia and variola viruses, have polymerases similar to eukaryotic α-polymerase rather than δ-polymerase, while adenovirus, herpes family viruses, and archaeotes have eukaryotic δ-like polymerases, suggesting that the eukaryotic α-polymerase gene is derived from a poxvirus-like organism, which had some eukaryote-like characteristics. Furthermore, the poxvirus's proliferation independent from the host-cell nucleus suggests the possibility that this virus could infect non-nucleated cells, such as ancestral eukaryotes. I wish to propose here a new hypothesis for the origin of the eukaryotic nucleus, posing symbiotic contact of an orthopoxvirus ancestor with an archaebacterium, whose genome already had a δ-like polymerase gene.

Key words: DNA polymerase α— DNA polymerase δ— DNA replication — Molecular evolution — Phylogenetic tree — Poxvirus — Eukaryotic nucleus 


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Copyright information

© Springer-Verlag New York Inc. 2001

Authors and Affiliations

  • Masaharu  Takemura
    • 1
  1. 1.Laboratory of Cancer Cell Biology, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 JapanJP

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