Alteration of nuclear-cytoplasmic trafficking is not only restricted to picornaviruses but has also been observed with negative strand viruses such as vesicular stomatitis virus (VSV) and influenza virus. Her and collaborators reported that RNA export and protein import are strongly inhibited by VSV matrix (M) protein, by microinjection of oocytes with radiolabeled RNAs and proteins. Radiolabeled tRNAs, mRNAs, U snRNAs, and rRNAs were injected directly into the nucleus of Xenopus laevis oocytes, and the subcellular localization of those RNAs was monitored by autoradiography. The conclusion of this work is that mRNA, U snRNA, and rRNA but not tRNA trafficking is blocked by VSV M protein [205] , in agreement with our findings on 2A proexpressing HeLa cells [17] . In addition, protein nuclear import was monitored by microinjection of radiolabeled proteins containing NLS in the oocytes cytoplasm. This assay revealed that VSV M protein abrogates protein nuclear import to the same extent as treatment with specific inhibitors of this pathway such as WGA [205] . These interesting findings support the idea that PV 2A pro and VSV M protein could target similar host proteins to impair macromolecule trafficking between nucleus and cytoplasm. In agreement with this possibility, it was found that the VSV M protein interacts with Nup98 [161] , which is one of the primary targets of PV 2A pro [16] . The N-terminal domain of VSV M is sufficient to block RNA nuclear export and aa 52-54 may play an essential role in this blockade, because their mutations to Ala completely abrogate this inhibitory effect. Indeed, the N-terminal domain of M protein is involved in the interaction with Nup98 and, in particular, aa 52-54, because their mutation to Ala blocks the binding of VSV M to Nup98 [161] . In addition, binding of M to Nup98 requires active mRNA export pathways since, treatment with inhibitors such as WGA hampers this interaction. VSV M is also able to induce the accumulation of endogenous polyadenylated mRNAs in the nucleus of HeLa cells, and this effect is prevented again by mutations in aa 52-54 of M [161] . Furthermore, VSV M interacts with Rae1, which plays an essential role in mRNA nuclear export by its interaction with Nup98 and mRNPs. Overexpression of either Nup98 or Rae-1 prevents the nuclear accumulation of polyadenylated mRNAs, suggesting that both factors may play a role in the blockade of mRNA nuclear export by VSV M protein [206] . Interestingly, IFN-γ specifically increases the level of both Nup98 and Rae-1 and indicates a potential antiviral effect of these proteins. Indeed, overexpression of both proteins by IFN-γ treatment counteracts the inhibitory effects of VSV M protein on mRNA nuclear export, highlighting the possibility of a crosstalk between M and IFN-γ that might control the fate of the viral replication in infected animals [201, 206] .