TRANSLATION REGULATION DURING HCMV INFECTION Public Deposited

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  • March 19, 2019
Creator
  • Ziehr, Benjamin
    • Affiliation: School of Medicine, Department of Microbiology and Immunology
Abstract
  • During viral infection competition for resources is inevitable. One of the fiercest areas of competition is mRNA translation. Host ribosomes are utilized by both host and viral mRNAs, since no virus encodes its own ribosome. Human Cytomegalovirus (HCMV) is a ubiquitous human pathogen that causes significant disease in newborns and immunocompromised individuals. While most viruses suppress host mRNA translation to limit competition for ribosomes, HCMV stimulates host mRNA translation. The goal of this dissertation is to investigate the mechanisms that allow HCMV mRNAs to efficiently compete for access to host ribosomes. mRNA translation begins with translation initiation, which is the rate limiting step of mRNA translation. To determine how viral mRNAs undergo translation initiation we investigated whether the host eIF4F translation initiation complex controlled HCMV mRNA translation. We found that despite eIF4F disruption that suppressed host mRNA translation, HCMV mRNAs continue to translated in the absence of eIF4F. To identify factors that may promote HCMV mRNA translation independent of eIF4F we performed a mass spectrometry screen for mRNA m7G cap binding proteins in HCMV infected cells. Two viral proteins were identified in our screen, pTRS1 and pIRS1. In addition to binding mRNA during infection, pTRS1 associates with the host translation machinery. We also demonstrated that pTRS1 is sufficient to preferentially stimulate translation of luciferase reporters containing viral sequences outside the context of infection. pTRS1 is a known inhibitor of the host antiviral kinase PKR. However, pTRS1 was able to stimulate translation in cells lacking PKR, indicating that pTRS1 has functions other than antagonizing PKR. Finally, we evaluated HCMV replication in the absence of pTRS1 or its redundant homolog pIRS1. Using a novel infection model we confirmed that either pTRS1 or pIRS1 is necessary to antagonize PKR for efficient HCMV replication. We also show that pTRS1 is necessary and sufficient to prevent stress granule formation. In fact pTRS1 can also prevent stress granule formation as a result of HRI activation suggesting that pTRS1 may antagonize HRI in addition to PKR. Using our novel infection system we also demonstrate the necessity of the PKR binding domain of pTRS1 for efficient HCMV replication.
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  • In Copyright
Advisor
  • Heise, Mark
  • Raab-Traub, Nancy
  • Lemon, Stanley
  • Moody, Cary
  • Moorman, Nathaniel
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2015
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  • Chapel Hill, NC
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