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Identification of an intercistronic internal ribosome entry site in a Marek's disease virus immediate-early gene

Abdessamad Tahiri-Alaoui1, Lorraine P Smith, Suzan Baigent

  • 1Division of Microbiology, Institute for Animal Health, Compton, Berkshire, United Kingdom. abdou.tahiri-alaoui@bbsrc.ac.uk

Journal of Virology
|March 20, 2009
PubMed

Insights

Researchers discovered an internal ribosome entry site (IRES) in Marek's disease virus (MDV). This IRES controls the translation of a specific protein (RLORF9) and its removal does not impact viral replication or mortality.

Area of Science:

  • Virology
  • Molecular Biology
  • Gene Expression

Background:

  • Marek's disease virus (MDV) is a highly infectious herpesvirus.
  • Understanding viral gene expression mechanisms is crucial for controlling infections.
  • Internal ribosome entry sites (IRES) are key elements in regulating translation, particularly in viruses.

Purpose of the Study:

  • To identify and characterize an internal ribosome entry site (IRES) in Marek's disease virus (MDV).
  • To investigate the function of the identified IRES in viral gene expression.
  • To assess the impact of IRES-mediated translation on viral replication and pathogenesis.

Main Methods:

  • Cloning and characterization of bicistronic mRNA from MDV-transformed cell lines (MSB-1).
  • Mapping the IRES to the intercistronic region (ICR) between two open reading frames (ORFs).
  • Deletion analysis to identify functional IRES elements within the ICR.
  • Reverse genetic experiments using an oncogenic strain of MDV type 1.

Main Results:

  • An IRES was identified in the intercistronic region (ICR) of a bicistronic mRNA from MDV.
  • The ICR functions as an IRES, enabling cap-independent translation of the second ORF (encoding RLORF9).
  • Deletion of the IRES-controlled RLORF9 did not significantly affect viral replication or MDV-induced mortality in experimental models.

Conclusions:

  • MDV utilizes an IRES element for the translation of essential viral proteins.
  • The identified IRES plays a role in regulating viral gene expression but is not essential for viral replication or virulence.
  • This finding provides insights into the complex translational strategies employed by herpesviruses.

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