Viral proteins are regulated post translationally by different mechanisms such as glycosylation, methylation and ubiquitination just to mention a few. In some flaviviruses, post translational modification of viral proteins by ubiquitin has diverse roles in viral life cycle and pathogenesis. In this study we found that Zika virus (ZIKV) precursor membrane (prM) protein is ubiquitinated on multiple lysine residues. Depletion of free cellular ubiquitin pools in ZIKV infected vero cells through treatment with proteasome inhibitor MG132, significantly suppressed egress of infectious viral particles, suggesting that ubiquitin proteasome system (UPS) is required for an efficient ZIKV replication cycle and in assembly of infectious virions. Additionally, we also demonstrate that prM protein is ubiquitinated through the UPS during ZIKV infection.
Co-expression of deubiquitinated prM mutant protein with E protein resulted in accumulation of viral proteins in lysates and diminishing secretion of viral proteins, suggeting that ubiquitination of prM protein also signals for interaction with E protein to form a prM-E protein heterodimer complex. Furthermore, data from immunofluorescence assays suggested that ubiquitination of prM protein is required for proper folding of E protein to form a relatively smooth heterodimer surface, albeit not for translocation of viral proteins into endoplasmic reticulum (ER) and trans-Golgi. Our results bring new instight of mechanisms involved in ZIKV replication biology that has to be explored further for possible application in development of potent vaccines and antiviral drugs against ZIKV infection that might be adopted into clinical setting.
