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Retroviruses and retrotransposons both insert copies of their genetic elements into the genome of the host cell. Thus, the viral genes are passed on when the host genome is replicated or translated. A typical retroviral DNA sequence contains 3-4 genes that encode the different proteins required for its structural assembly and function as a molecular parasite. This DNA is transcribed into a single mRNA, which is very similar in structure to conventional mRNAs, i.e., it is capped at the 5’...
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The origin of viruses.

Patrick Forterre1, David Prangishvili

  • 1Institut de Génétique et Microbiologie, Université Paris-Sud, CNRS UMR 8621, 91405 Orsay Cedex, France. forterre@pasteur.fr

Research in Microbiology
|August 4, 2009
PubMed
Summary
This summary is machine-generated.

Viruses are ancient, with unique genes originating in the virosphere, not solely from cellular theft. The independent evolution of virions before the Last Universal Cellular Ancestor challenges current origin theories.

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Area of Science:

  • Virology
  • Evolutionary Biology
  • Molecular Biology

Background:

  • Viruses are obligate intracellular parasites that replicate within host cells.
  • Traditional views suggest viruses acquired genes from host cells.
  • Emerging evidence indicates a more complex and ancient origin for viral components.

Purpose of the Study:

  • To challenge the traditional view of viruses as mere gene pickpockets.
  • To explore the ancient origins of viral proteins and virions.
  • To highlight the unexplained emergence of virions as a gene dissemination mechanism.

Main Methods:

  • Comparative genomics to analyze viral protein homologues.
  • Structural analysis of viral capsid proteins.
  • Phylogenetic analysis to infer evolutionary history.

Main Results:

  • Most viral proteins lack homologues in modern cellular life.
  • Viral genes likely originated within the virosphere or from extinct cellular lineages.
  • Evidence suggests at least two virion types evolved independently before the Last Universal Cellular Ancestor (LUCA).

Conclusions:

  • Viruses are ancient entities with unique genetic origins.
  • The independent evolution of virions predates the LUCA.
  • The specific evolutionary pathways leading to virion formation remain an open question.