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Related Experiment Videos

A new model for coronavirus transcription

S G Sawicki1, D L Sawicki

  • 1Department of Microbiology and Immunology, Medical College of Ohio, Toledo 43699, USA.

Advances in Experimental Medicine and Biology
|October 23, 1998
PubMed
Summary

Coronaviruses use a novel discontinuous RNA synthesis mechanism. New evidence supports the 3' discontinuous extension of negative strands model for subgenomic mRNA production, challenging the leader-primed transcription theory.

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Area of Science:

  • Virology
  • Molecular Biology
  • RNA Synthesis

Background:

  • Coronaviruses possess a large positive-sense RNA genome with a 5' cap and 3' polyadenylation.
  • Infected cells contain subgenomic mRNAs (sgmRNAs) forming a nested set with the genome, sharing a common 5' leader sequence.
  • The mechanism of coronavirus sgmRNA transcription, particularly discontinuous transcription, remains poorly understood and debated.

Purpose of the Study:

  • To investigate and propose a new model for coronavirus transcription, termed 3' discontinuous extension of negative strands.
  • To challenge the existing leader-primed transcription model by identifying and characterizing key intermediate RNA structures.

Main Methods:

  • Identification and separation of replication intermediates (RIs) containing subgenome-length RNA from those with genome-length templates.
  • Analysis of the timing of subgenome-length negative strand formation during viral infection.
  • Characterization of the 3' end sequences of subgenome-length negative strands, specifically the presence of a leader RNA copy.

Main Results:

  • Replication intermediates with subgenome-length templates were found in infected cells and are distinct from genome-length RIs.
  • Subgenome-length negative strands form early in infection, coinciding with increased viral RNA synthesis.
  • These negative strands contain a complementary copy of the 5' leader RNA at their 3' end, crucial for sgmRNA synthesis.

Conclusions:

  • The study provides evidence supporting the 3' discontinuous extension of negative strands model for coronavirus transcription.
  • This new model suggests negative strand synthesis is discontinuous, while subgenomic mRNA synthesis is continuous, reversing the leader-primed model's predictions.
  • Subgenome-length negative strands arise directly from the genome and acquire their leader sequence via polymerase jumping.

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