title: Protein methylation is required to maintain optimal HIV-1 infectivity.
abstract: BACKGROUND
  Protein methylation is recognized as a major protein modification pathway regulating diverse cellular events such as protein trafficking, transcription, and signal transduction. More recently, protein arginine methyltransferase activity has been shown to regulate HIV-1 transcription via Tat. In this study, adenosine periodate (AdOx) was used to globally inhibit protein methyltransferase activity so that the effect of protein methylation on HIV-1 infectivity could be assessed.
  
  
  RESULTS
  Two cell culture models were used: HIV-1-infected CEM T-cells and HEK293T cells transfected with a proviral DNA plasmid. In both models, AdOx treatment of cells increased the levels of virion in culture supernatant. However, these viruses had increased levels of unprocessed or partially processed Gag-Pol, significantly increased diameter, and displayed reduced infectivity in a MAGI X4 assay. AdOx reduced infectivity equally in both dividing and non-dividing cells. However, infectivity was further reduced if Vpr was deleted suggesting virion proteins, other than Vpr, were affected by protein methylation. Endogenous reverse transcription was not inhibited in AdOx-treated HIV-1, and infectivity could be restored by pseudotyping HIV with VSV-G envelope protein. These experiments suggest that AdOx affects an early event between receptor binding and uncoating, but not reverse transcription.
  
  
  CONCLUSIONS
  Overall, we have shown for the first time that protein methylation contributes towards maximal virus infectivity. Furthermore, our results also indicate that protein methylation regulates HIV-1 infectivity in a complex manner most likely involving the methylation of multiple viral or cellular proteins and/or multiple steps of replication.
authors.affiliation: Division of Immunology and Infectious Disease, Queensland Institute of Medical Research, Brisbane, Queensland, 4006, Australia. nicoleW@qimr.edu.au
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Willemsen
authors.forename: Eleanor M
authors.initials: EM
authors.lastname: Hitchen
authors.forename: Tracey J
authors.initials: TJ
authors.lastname: Bodetti
authors.forename: Ann
authors.initials: A
authors.lastname: Apolloni
authors.forename: David
authors.initials: D
authors.lastname: Warrilow
authors.forename: Sabine C
authors.initials: SC
authors.lastname: Piller
authors.forename: David
authors.initials: D
authors.lastname: Harrich
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D015685:Fusion Proteins, gag-pol / Q000378:metabolism; D016336:Gene Products, vpr / Q000378:metabolism; D015497:HIV-1 / Q000187:drug effects / Q000472:pathogenicity* / Q000648:ultrastructure; D006367:HeLa Cells; D006801:Humans; D008745:Methylation; D008780:Methyltransferases / Q000037:antagonists & inhibitors*; D010504:Periodic Acid / Q000494:pharmacology*; D011506:Proteins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000821:virology; D014771:Virion / Q000187:drug effects / Q000378:metabolism; D054325:vpr Gene Products, Human Immunodeficiency Virus
chemical_list: D015685:Fusion Proteins, gag-pol; D016336:Gene Products, vpr; D011506:Proteins; D054325:vpr Gene Products, Human Immunodeficiency Virus; D010504:Periodic Acid; C009288:metaperiodate; D008780:Methyltransferases; D000241:Adenosine