Model suggesting that replication of influenza virus is regulated by stabilization of replicative intermediates.
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ABSTRACT:
SUBMITTER: Vreede FT
PROVIDER: S-EPMC506943 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Reassortment of influenza viral RNA (vRNA) segments in co-infected cells can lead to the emergence of viruses with pandemic potential. Replication of influenza vRNA occurs in the nucleus of infected cells, while progeny virions bud from the plasma membrane. However, the intracellular mechanics of vRNA assembly into progeny virions is not well understood. Here we used recent advances in microscopy to explore vRNA assembly and transport during a productive infection. We visualized four distinct vRNA segments within a single cell using fluorescent in situ hybridization (FISH) and observed that foci containing more than one vRNA segment were found at the external nuclear periphery, suggesting that vRNA segments are not exported to the cytoplasm individually. Although many cytoplasmic foci contain multiple vRNA segments, not all vRNA species are present in every focus, indicating that assembly of all eight vRNA segments does not occur prior to export from the nucleus. To extend the observations made in fixed cells, we used a virus that encodes GFP fused to the viral polymerase acidic (PA) protein (WSN PA-GFP) to explore the dynamics of vRNA assembly in live cells during a productive infection. Since WSN PA-GFP colocalizes with viral nucleoprotein and influenza vRNA segments, we used it as a surrogate for visualizing vRNA transport in 3D and at high speed by inverted selective-plane illumination microscopy. We observed cytoplasmic PA-GFP foci colocalizing and traveling together en route to the plasma membrane. Our data strongly support a model in which vRNA segments are exported from the nucleus as complexes that assemble en route to the plasma membrane through dynamic colocalization events in the cytoplasm.
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Project description:[This corrects the article DOI: 10.1371/journal.ppat.1003971.].
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Project description:Ultraviolet (UV)-induced DNA damage causes an efficient block of elongating replication forks. The checkpoint kinase, CHK1 has been shown to stabilize replication forks following hydroxyurea treatment. Therefore, we wanted to test if the increased UV sensitivity caused by the unspecific kinase inhibitor caffeine--inhibiting ATM and ATR amongst other kinases--is explained by inability to activate the CHK1 kinase to stabilize replicative structures. For this, we used cells deficient in polymerase ? (Pol?), a translesion synthesis polymerase capable of properly bypassing the UV-induced cis-syn TT pyrimidine dimer, which blocks replication. These cells accumulate gaps behind progressing replication forks after UV exposure. We demonstrate that both caffeine and CHK1 inhibition, equally retards continuous replication fork elongation after UV treatment. Interestingly, we found more pronounced UV-sensitization by caffeine than with the CHK1 inhibitor in clonogenic survival experiments. Furthermore, we demonstrate an increased collapse of replicative structures after caffeine treatment, but not after CHK1 inhibition, in UV-irradiated cells. This demonstrates that CHK1 activity is not required for stabilization of gaps induced during replication of UV-damaged DNA. These data suggest that elongation and stabilization of replicative structures at UV-induced DNA damage are distinct mechanisms, and that CHK1 is only involved in replication elongation.
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Project description:Influenza virus neuraminidase (NA), a type II transmembrane glycoprotein, is transported to the virus assembly site at the plasma membrane and is a major viral envelope component that plays a critical role in the release of progeny virions and in determination of host range restriction. Although signals/sequences in NA for translocation, sorting and raft association have been identified, little is known about the host factors that are involved in regulating the intracellular and cell surface transport of NA. In this report, we have investigated the involvement of Rho family GTPases in NA transport to the cell surface. We found that expression of constitutively active or inactive mutants of RhoA or Rac1 did not significantly affect the amount of NA that reached the cell surface. Interestingly, expression of constitutively active Cdc42 or depletion of the Cdc42-specific GAP, ARHGAP21, promoted the transport of NA to the plasma membranes. By contrast, cells expressing shRNA targrting Cdc42 or overexpressing ARHGAP21 exhibited a significant decrease in the amount of cell surface-localized NA. Furthermore, silencing of Cdc42 or ARHGAP21 had significant effects on influenza A virus replication. Together, our results reveal that ARHGAP21 and Cdc42-based signaling regulates the NA transport and thereby impacts virus replication. This microarray experiment was carried out to find out whether Cdc42 and ARHGAP21 expression levels in A549 cell were changed after WSN infection.
2012-04-04 | GSE32878 | GEO
Project description:Influenza virus neuraminidase (NA), a type II transmembrane glycoprotein, is transported to the virus assembly site at the plasma membrane and is a major viral envelope component that plays a critical role in the release of progeny virions and in determination of host range restriction. Although signals/sequences in NA for translocation, sorting and raft association have been identified, little is known about the host factors that are involved in regulating the intracellular and cell surface transport of NA. In this report, we have investigated the involvement of Rho family GTPases in NA transport to the cell surface. We found that expression of constitutively active or inactive mutants of RhoA or Rac1 did not significantly affect the amount of NA that reached the cell surface. Interestingly, expression of constitutively active Cdc42 or depletion of the Cdc42-specific GAP, ARHGAP21, promoted the transport of NA to the plasma membranes. By contrast, cells expressing shRNA targrting Cdc42 or overexpressing ARHGAP21 exhibited a significant decrease in the amount of cell surface-localized NA. Furthermore, silencing of Cdc42 or ARHGAP21 had significant effects on influenza A virus replication. Together, our results reveal that ARHGAP21 and Cdc42-based signaling regulates the NA transport and thereby impacts virus replication. This microarray experiment was carried out to find out whether Cdc42 and ARHGAP21 expression levels in A549 cell were changed after WSN infection. Total RNAs were extracted from three different groups of A549 cells that had been infected with or without WSN for 10 h, using TRIzol reagent (Invitrogen, Carlsbad, CA). Samples were amplified and labeled using a NimbleGen One-Color DNA Labeling Kit.
2012-04-03 | E-GEOD-32878 | biostudies-arrayexpress