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Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus
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Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus

Published on: July 27, 2021

Cytomegalovirus assemblin (pUL80a): cleavage at internal site not essential for virus growth; proteinase absent from

Chee-Kai Chan1, Edward J Brignole, Wade Gibson

  • 1Virology Laboratories, Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

Journal of Virology
|August 7, 2002
PubMed

Insights

Human cytomegalovirus (HCMV) maturational proteinase cleavage at the internal (I) site is not essential for infectious virus production. Blocking I-site cleavage did not affect virus yield or particle formation in HCMV-infected cells.

Area of Science:

  • Virology
  • Molecular Biology
  • Structural Biology

Background:

  • Human cytomegalovirus (HCMV) utilizes a 74-kDa precursor proteinase for self-cleavage at four sites.
  • Two sites (M and R) are conserved across herpesviruses, while two others (I and C) are specific to CMV and located within the assemblin domain.

Purpose of the Study:

  • To investigate the necessity of internal (I) site cleavage of assemblin during HCMV infection.
  • To determine the impact of a blocked I-site mutation on viral replication and particle composition.

Main Methods:

  • Utilized the CMV-bacterial artificial chromosome system to engineer a mutant virus with a blocked I-site (Ala143 to Val).
  • Characterized the mutant virus for I-site cleavage efficiency, viral production rates, and particle content (virions, NIEPs, dense bodies).
  • Analyzed the presence of assemblin and its cleavage products in noninfectious enveloped particles (NIEPs) and virions.

Main Results:

  • Confirmed successful mutation and lack of I-site cleavage in infected cells.
  • Observed no significant impact on virus production rates or particle yields.
  • Found assemblin and cleavage products in NIEPs but not in mature HCMV virions.
  • Demonstrated increased abundance of the C-site cleavage product in mutant-infected cells and NIEPs.

Conclusions:

  • HCMV production of infectious virions does not require I-site cleavage of assemblin.
  • Assemblin is not a necessary component of the mature HCMV virion.

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