Antiviral effect of the cellular promyelocytic leukemia protein against dengue and Junín RNA viruses

C. C. GARCÍA; GIOVANNONI, F; CARRO, AC; DAMONTE E.B.

Minneapolis

Congreso; 30th Annual Meeting, American Society for Virology; 2011

ASV

Promyelocytic leukemia (PML) nuclear bodies (NBs) are discrete nuclear foci that contain several cellular proteins involved in diverse processes such as transcription, chromatin structure, DNA repair, apoptosis and antiviral responses against a number of viruses. Accumulating reports have revealed various strategies developed by DNA viruses to disrupt PML NBs. However, very little information is available about how RNA viruses affect PML NBs. Here we investigated the antiviral role of PML in the replication of two hemorrhagic fever causing RNA viruses of great importance in public health, dengue (DENV) and Junin (JUNV) viruses. To evaluate the effect of PML on infectious DENV and JUNV production, A549 cells were transfected with PML-siRNA, and 24 h later cultures were infected with the respective virus at a MOI of 0.1. Supernatants were collected at 24 h p.i. and titrated by plaque assay. Results showed that PML silencing rendered A549 cells more susceptible to both RNA viruses. The virus yields observed were 90 and 70 % higher for DENV and JUNV, respectively, in comparison with virus yields obtained in non-transfected cells. Moreover, confocal images of infected cells have shown that nuclear PML underwent a dramatic rearrangement during DENV infection becoming more distinct, with increased numbers and size of PML NBs. On the other hand, the effect observed in JUNV infected cells was different and included the disruption of PML NBs, surrounded by diffuse fluorescence in the vicinity of the original structure, suggesting a marked efflux of PML protein from the nucleus to the cytoplasm, in comparison with uninfected cells. Different RNA viruses differ much in their abilities to induce IFN. Our results suggest that the differential antiviral effect of PML on DENV and JUNV viruses depends on the specific role of PML in mediating an IFN-induced antiviral state and also suggests but does not prove that PML NBs structures have any role in the establishment of persistence arenavirus infection. In conclusion, this is the first brief report of the variable susceptibility of RNA viruses to human PML proteins. The exact mechanism behind PML-mediated intracellular defense against DENV and JUNV, and the strategy by which these viruses evade this cellular defense mechanism requires further study.