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slgoogin8981

Virus-Mediated Compartmentalization of the Host Translational Machinery - 22 views

mbio.asm.org/...e01463-14.full

shared by slgoogin8981 on 27 Oct 14 - No Cached
  • Similarly, the viral single-stranded RNA binding protein σNS localized to the factory margins and had a tubulovesicular staining pattern that extended a short distance from the margins of the factories and colocalized with endoplasmic reticulum (ER) markers.
    • nleonard11
      nleonard11 on 29 Oct 14
       
      This reovirus has single-stranded RNA rather than double stranded. Research. σNS is a binding protein that has an affinitiy for single-stranded RNA. Why is it used for doulbe-stranded RNA.
  • We further show that the nonstructural protein σNS strongly colocalizes and immunoprecipitates with two proteins in the 43S preinitiation complex (PIC), eIF3A and pS6R, suggesting a role for σNS in the recruitment or maintenance of ribosomes within VF.
    • laceemarie
      laceemarie on 31 Oct 14
       
      If σNS is involved in ribosome recruitment and/or maintenance, this seems like a good target for an antiviral therapy. 
  • This model implies that newly synthesized viral proteins must, by some mechanism(s), be trafficked back into the factory to participate in replication and assembly. Data supporting this model are limited.
    • laceemarie
      laceemarie on 31 Oct 14
       
      "Limited," but still exists. So under what circumstances did/could this happen? Could it be a possible way to avoid an antiviral drug that inhibits σNS?
  • ...8 more annotations...
  • Within the VF, viral core particles transcribe and release viral mRNAs that possess a dimethylated cap 1 structure at the 5′ terminus but lack a poly(A) tail (19).
    • alexridesducati
      alexridesducati on 31 Oct 14
       
      It seems that Reovirus recruits host proteins in order to replicate, and in this sentence we see that the viral mRNAs use a dimethlyated cap vs. the traditional host methylguanosine cap. Does this have any sort of impact on initiation factors associated with the ribosome? The viral mRNA also seems to be lacking in a poly-A tail. Is it because the mRNAs are created in a VF that they dont need to worry about having one?
    • abachman12
      abachman12 on 21 Nov 14
       
      I was also thinking the same thing. Does this have any effects on the initiation factors in whole? Does it change anything or do anything different than normal?
  • Consistent with our findings, the authors noted that the rough endoplasmic reticulum (RER) made numerous contacts with VF, which they suggested may indicate a role for RER in the transport of newly synthesized viral proteins to the VF, as is the case for rubella virus (64).
    • joeyevenson
      joeyevenson on 31 Oct 14
       
      The rough endoplasmic reticulum may be involved in the transport of newly synthesizes viral proteins to the viral factory, could an antiviral that targets the endoplasmic reticulum prevent these newly synthesized proteins from ever getting that far? Does the host do this as a response to the virus? Or is it the virus controlling the cell to transport the viral proteins?
  • To address this, we monitored protein expression levels of eIF4E, eIF4A1, and eIF4G over the course of an infection. As others have found (39), we were unable to detect any difference in the levels of total protein in mock versus infected cells from 0 to 20 h p.i. (Fig. 3C and data not shown). Together, these data suggest that cellular translation proteins are redistributed to the VF.
    • becky214
      becky214 on 31 Oct 14
       
      I am confused as to how the data is showing that these proteins are redistributed to the VF.
  • Most reovirus strains form filamentous VF through an association with stabilized microtubules. However, the T3D strain used in these experiments contains a temperature-sensitive mutation in the viral protein μ2 that prevents this association, resulting in the production of globular VF at 37°C (27, 28). Therefore, to evaluate if PMY labeling occurs within filamentous viral factories, we infected cells with the serotype 1 Lang (T1L) strain. As we found for T3D-infected cells, the PMY labeling localized to T1L VF at 18 h postinfection
    • rmeloche10
      rmeloche10 on 31 Oct 14
       
      Is this temperature sensitive mutation put in place by the authors? Or is the mutation a natural feature of the virus, if it is would there be any reason for inhibiting the micro tubule stabalization? 
  • It was unclear if this was a result of increased expression levels or as a consequence of redistribution of the proteins to the factories. To address this, we monitored protein expression levels of eIF4E, eIF4A1, and eIF4G over the course of an infection. As others have found (39), we were unable to detect any difference in the levels of total protein in mock versus infected cells from 0 to 20 h p.i. (Fig. 3C and data not shown). Together, these data suggest that cellular translation proteins are redistributed to the VF.
    • Sean Hogan
      Sean Hogan on 31 Oct 14
       
      I had a little trouble wrapping my brain around this part. If the IF proteins are expressed at similar levels then what is the cause of the redistribution? Does it have to do with the sigma NS interaction and then eventually the preinitiation complex is recruited?
  • Our finding that σNS interacts with eIF3A and pS6R suggests that translational machinery is recruited to the factory by viral proteins. This is consistent with the finding of others that σNS cosediments with 40S and 60S ribosomes (62) and suggests that σNS is directly involved in viral translation.
    • Sean Hogan
      Sean Hogan on 31 Oct 14
       
      I feel like a  loss of function experiment (sigma NS) would provide an answer for this.  
  • FIG 3  Cellular translation initiation factors colocalize to viral factories. (A, B) CV-1 cells were infected with T3D or T1L at an MOI of 1. At 18 h p.i., RPM-labeled cells were coimmunostained for μNS and eIF4E (A) or eIF3A (B). Scale bars, 10 µm. (C) CV-1 cells were infected with T3D, MOI of 3, for the times indicated. Protein levels were assessed by immunoblotting. M = mock.
    • apopp10
      apopp10 on 31 Oct 14
       
      I am having trouble interpreting both this figure and figure 4 immediately following it. How do these figures exactly support the claim that transcription initiation, elongation, termination and recycling factors are recruited to viral factories?
    • slgoogin8981
      slgoogin8981 on 19 Nov 14
       
      Does the viral factor protect the dsRNA from RIG-1? Earlier the paper spoke of energy balances, does the viral factor require a lot of energy to be created?
  • jpolanco10 on 28 Oct 14
     
    Focus paper for friday
  • nleonard11 on 31 Oct 14
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