STORIES ON DENGUE VIRUS AND HOST CELL pre-mRNA PROCESSING

POZZI, BERTA; TORTI, M FLORENCIA; VAZ DRAGO, RITA; GAIOLI, NICOLAS; GEBHARD, LEOPOLDO; IGLESIAS, GABRIEL; GAMARNIK, ANDREA V; GARCIA, CYBELE; SREBROW, ANABELLA

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress; 2019

SAIB y PABMB

Dengue virus is a highly prevalent human pathogen transmitted by Aedes aegypti and Aedes albopictus mosquitoes. This virus presents a sense and single­stranded RNA genome that encodes for a limited set of proteins, depending on the host cell machinery for productive replication. While eukaryotic cells rely on innate immune responses to protect from viral infection, viruses have evolved sophisticated mechanisms of evasion that counteract the antiviral response. Undoubtedly, understanding this complex interplay is of paramount importance for the proper design of antiviral therapies.Few years ago, in collaboration with the Gamarnik laboratory, we reported a link between dengue infection and host cell splicing machinery, mainly the intrusion of the viral protein NS5 in the cellular spliceosome. In RNA­seq experiments from human cells infected with dengue, we observed severe alterations of the splicing process, basically an enrichment of intronic sequences and changes in alternative splicing patterns. In particular, we noted that the transcript of the SAT1 gene, of well­ known antiviral action, evidences higher inclusion of alternative exon 4 in infected cells. This exon4­containing SAT1 mRNA isoform is targeted for degradation by non­sense mediated decay, whereas the exon 4­lacking variant codes for a spermidine/spermine acetyl­transferase enzyme that decreases the reservoir of these polyamines in the cell, limiting viral replication. Delving into the molecular mechanism responsible for the alternative splicing change in SAT1 pre­mRNA upon viral infection, we observed that this condition decreases protein levels of RBM10, a splicing factor responsible for SAT1 exon 4 skipping. We found that the dengue polymerase NS5 interacts with RMB10 and triggers its degradation in a proteasome­dependent manner. Moreover, RBM10 over­expression in infected cells prevents SAT1 splicing change and also decreases viral replication, while knock­ down of this splicing factor not only enhances the splicing change but also benefit viral replication. These results lead us to propose an anti­viral role for RBM10. In addition, RBM10 depletion attenuates the infection-triggered transcriptional induction of interferon and pro­inflammatory cytokines. Currently, we hypothesize that RBM10 may be exerting its anti viral role not only via its already well documented activity as a splicing regulator but also by modulating the innate immune response through impinging the signaling pathway downstream of the viral sensor protein RIG-I.