Differential effect of acute and persistent Junín virus infections on the nucleo-cytoplasmic trafficking and expression of heterogeneous nuclear ribonucleoproteins type A and B

Abstract

Heterogeneous nuclear ribonucleoproteins A and B (hnRNPs A/B), cellular RNA-binding proteins that participate in splicing, trafficking, translation and turnover of mRNAs, have been implicated in the life cycles of several cytoplasmic RNA viruses. Here, we demonstrate that silencing of hnRNPs A1 and A2 significantly reduces the replication of the arenavirus Junín virus (JUNV), the aetiological agent of Argentine haemorrhagic fever. While acute JUNV infection did not modify total levels of expression of hnRNPs A/B in comparison with uninfected cells, non-cytopathic persistent infection exhibited low levels of these cell proteins. Furthermore, acutely infected cells showed a cytoplasmic relocalization of overexpressed hnRNP A1, probably related to the involvement of this protein in virus replicative cycle. This cytoplasmic accumulation was also observed in cells expressing viral nucleoprotein (N), and co-immunoprecipitation studies revealed the interaction between hnRNP A1 and N protein. By contrast, a predominantly nuclear distribution of overexpressed hnRNP A1 was found during persistent infection, even in the presence of endogenous or overexpressed N protein, indicating a differential modulation of nucleo-cytoplasmic trafficking in acute and persistent JUNV infections. INTRODUCTIONJunín virus (JUNV), a member of the family Arenaviridae, is the aetiological agent of Argentine haemorrhagic fever. These enveloped ssRNA viruses have a genome consisting of two RNA segments: the S segment encodes the structural nucleoprotein (N) and the glycoprotein precursor (GPC), which is secondarily cleaved into the envelope proteins G1 and G2; and the L segment encodes the viral polymerase (L) and a zinc-binding matrix protein (Z). Besides JUNV, other arenaviruses such as Lassa, Machupo, Guanarito and Sabiá viruses also cause severe haemorrhagic diseases in man. Specific rodents are the principal hosts of the arenaviruses and humans may become infected through direct contact with infected rodents or through inhalation of infectious rodent excreta and secreta (Charrel & de Lamballerie, 2010;Yun et al., 2008).JUNV establishes a persistent infection in its main reservoir in nature, the cricetid Calomys musculinus, or in cell cultures (Ellenberg et al., 2002(Ellenberg et al., , 2004(Ellenberg et al., , 2007. Persistent infection in Vero cells is achieved after the acute phase of infection, which is characterized by the production of high titres of infectious virus and a marked cytopathic effect. During persistence cells remain unable to produce infectious virus, with a continuous synthesis of virus nucleoprotein (N) associated with blockage of the expression of the glycoprotein G1 and absence of cytopathic action (Ellenberg et al., 2002(Ellenberg et al., , 2004. Little is known about the cell components involved in JUNV replication during acute infection or in the establishment and maintenance of persistent infection.Several cytoplasmic RNA viruses alter the nucleo-cytoplasmic trafficking of cellular RNA and proteins and this may fac...

Downregulation of Nipah Virus N mRNA Occurs through Interaction between Its 3′ Untranslated Region and hnRNP D

“…Similar relocalizations of hnRNP A1, C1/C2, and K were also reported (24). In addition to VSV, other RNA viruses, such as enterovirus (25,26), rhinovirus (27), Japanese encephalitis virus (28), and Junin virus (29), have also been shown to relocalize hnRNP proteins. To the best of our knowledge, relocalization of hnRNP proteins by NiV infection has not been reported previously.…”

Host Cell Factors as Antiviral Targets in Arenavirus Infection

“…The first report providing evidence about the importance of hnRNPs on JUNV replication was a comparative study of acute and persistent JUNV infections performed in Vero cell cultures [73]. Silencing of hnRNP A1 or hnRNP A2, by using small interfering RNAs (siRNAs), caused a decrease in JUNV protein synthesis and progeny virus production during acute infection.…”

“…These results indicate that hnRNP A1 would favor JUNV productive infection through the interaction with the nucleoprotein. On the other hand, JUNV non-productive persistent infection might involve downregulation of hnRNPs A/B, as well as changes in nucleo-cytoplasmic trafficking [73]. …”

“…The inhibition of Akt phosphorylation by the PI3K inhibitor Ly294002 impaired virus production in different cell types indicating the essential role of PI3K/Akt signaling for JUNV infection. In view that PI3K/Akt activation is also involved in the stabilization of the mRNA encoding hnRNPA1 [85] and taking into account, as previously mentioned, the participation of this factor during JUNV replication [73], it is tempting to speculate that activation of this pathway may contribute in other stages of virus multiplication besides virus uptake. …”

Regulation of Tacaribe Mammarenavirus Translation: Positive 5′ and Negative 3′ Elements and Role of Key Cellular Factors

“…This region contains potential recognition sites for RNA binding proteins (RBP), such as heterogeneous nuclear ribonucleoproteins (hnRNPs) (RBPmap [http://rbpmap.technion.ac.il/]). Interestingly, it has been reported that silencing of a number of hnRNPs, known to regulate translation, reduces virus yield in JUNV-infected cells, suggesting that hnRNPs might be required during infection (27,28). We speculate that the 5= conserved terminal motif (or eventually the terminal stem-loop) in concert with the internal UTR sequence harboring RBP recognition site(s) might facilitate the recruitment of the 43S preinitiation complex to viral mRNA.…”