Dengue Virus Genome Uncoating Requires Ubiquitination

N.GABRIEL IGLESIAS; MARIO ROSSI; LAURA A. BYK; LEOPOLDO G. GEBHARD; FEDERICO A. DE MAIO; ANDREA V. GAMARNIK

mBio

ASM

Año: 2016 vol. 7 p. 1 - 10

2150-7511

The process of genome release or uncoating after viral entry is one of the least studied steps in the flavivirus life cycles. Flaviviruses are mainly arthropod-borne viruses including emerging and re-emerging pathogens such as dengue, Zika and West Nile viruses. Currently, dengue is one of the most significant human viral pathogens transmitted by mosquitoes, responsible for about 390 million infections every year around the world. Here, we examined for the first time molecular aspects of dengue virus genome uncoating. We followed the fate of the capsid protein and RNA genome early during infection and found that capsid is degraded after viral internalization by the host ubiquitin-proteasome system. However, proteasome activity and capsid degradation were not necessary to free the genome for initial viral translation. Unexpectedly, genome uncoating was blocked by inhibiting ubiquitination. Using different assays to bypass entry and evaluate the first rounds of viral translation, a narrow window of time during infection that requires ubiquitination but not proteasome activity was identified. In this regard, ubiquitin E1 activating enzyme inhibition was sufficient to stabilize the incoming viral genome in the cytoplasm of infected cells, causing its retention either in endosomes or nucleocapsids. Our studies support a model in which dengue virus genome uncoating requires a non-degradative ubiquitination step, providing new insights on this crucial but understudied viral process.