Vesicular stomatitis virus (VSV) matrix
protein inhibits nuclear-cytoplasmic
mRNA transport. The goal of this work is to determine whether VSV inhibits the nuclear-cytoplasmic transport of heterogeneous
ribonucleoproteins (hnRNPs), which are thought to serve as
mRNA export factors. Confocal microscopy experiments showed that hnRNPA1, hnRNPK, and hnRNPC1/C2, but not hnRNPB1 or
lamin A/C, are relocalized to the cytoplasm during VSV
infection. We determined whether
protein import is inhibited by VSV by transfecting cells with a plasmid encoding
enhanced green fluorescent protein (EGFP) tagged with either the M9 nuclear localization sequence (NLS) or the classical NLS. These experiments revealed that both the M9 NLS and the classical NLS are functional during VSV
infection. These data suggest that the inhibition of
protein import is not responsible for
hnRNP relocalization during VSV
infection but that
hnRNP export is enhanced. We found that hnRNPA1 relocalization was significantly reduced following the silencing of the
mRNA export factor Rae1, indicating that Rae1 is necessary for
hnRNP export. In order to determine the role of hnRNPA1 in VSV
infection, we silenced hnRNPA1 in HeLa cells and assayed three aspects of the viral life cycle: host
protein synthesis shutoff concurrent with the onset of
viral protein synthesis, replication by plaque assay, and cell killing. We observed that host shutoff and replication are unaffected by the reduction in hnRNPA1 but that the rate of VSV-induced apoptosis is slower in cells that have reduced hnRNPA1. These data suggest that VSV promotes hnRNPA1 relocalization in a Rae1-dependent manner for apoptotic signaling.