Murine gammaherpesvirus 68 ORF75c contains ubiquitin E3 ligase activity and requires PML SUMOylation but not other known cellular PML regulators, CK2 and E6AP, to mediate PML degradation

Virology. 2013 Jun 5;440(2):140-9. doi: 10.1016/j.virol.2013.02.014. Epub 2013 Mar 27.


All gammaherpsviruses encode at least one gene related to the cellular formylglycinamide ribonucleotide amidotransferase (FGARAT) enzyme but their biological roles are relatively unknown. The murine gammaherpesvirus 68 (MHV68) vFGARAT, ORF75c, mediates a proteasome-dependent degradation of the antiviral promyelocytic leukemia (PML) protein by an unknown mechanism, which is addressed in this study. We found that ORF75c interacts weakly with PML and SUMO-modified forms of PML are important for its degradation by ORF75c. ORF75c-mediated PML degradation was not dependent on two known cellular regulators of PML stability, Casein kinase II (CK2) and human papilloma virus E6-associated protein (E6AP). Finally, ORF75c had self-ubiquitination activity in vitro and its expression increased levels of ubiquitinated PML in transfected cells. Taken together, the evidence accumulated in this study provides new insights into the function of a vFGARAT and is consistent with a model in which ORF75c could mediate direct ubiquitination of PML resulting in its degradation by the proteasome.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor / metabolism*
  • Cell Line
  • Host-Pathogen Interactions*
  • Humans
  • Mice
  • Nuclear Proteins / metabolism*
  • Promyelocytic Leukemia Protein
  • Protein Interaction Mapping
  • Protein Processing, Post-Translational*
  • Proteolysis
  • Rhadinovirus / physiology*
  • Sumoylation*
  • Transcription Factors / metabolism*
  • Tumor Suppressor Proteins / metabolism*
  • Ubiquitin-Protein Ligases / metabolism*


  • Nuclear Proteins
  • Pml protein, mouse
  • Promyelocytic Leukemia Protein
  • Transcription Factors
  • Tumor Suppressor Proteins
  • Ubiquitin-Protein Ligases
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor
  • phosphoribosylformylglycinamidine synthetase