| 1. |
- Ahlgren-Berg, Alexandra, et al.
(författare)
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A comparative analysis of the bifunctional Cox proteins of two heteroimmune P2-like phages with different host integration sites
- 2009
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Ingår i: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 385:2, s. 303-12
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Tidskriftsartikel (refereegranskat)abstract
- The Cox protein of the coliphage P2 is multifunctional; it acts as a transcriptional repressor of the Pc promoter, as a transcriptional activator of the P(LL) promoter of satellite phage P4, and as a directionality factor for site-specific recombination. The Cox proteins constitute a unique group of directionality factors since they couple the developmental switch with the integration or excision of the phage genome. In this work, the DNA binding characteristics of the Cox protein of WPhi, a P2-related phage, are compared with those of P2 Cox. P2 Cox has been shown to recognize a 9 bp sequence, repeated at least 6 times in different targets. In contrast to P2 Cox, WPhi Cox binds with a strong affinity to the early control region that contains an imperfect direct repeat of 12 nucleotides. The removal of one of the repeats has drastic effects on the capacity of WPhi to bind to the Pe-Pc region. Again in contrast to P2 Cox, WPhi Cox has a lower affinity to attP compared to the Pe-Pc region, and a repeat of 9 bp can be found that has 5 bp in common with the repeat in the Pe-Pc region. WPhi Cox, however, is essential for excisive recombination in vitro. WPhi Cox, like P2 Cox, binds cooperatively with integrase to attP. Both Cox proteins induce a strong bend in their DNA targets upon binding.
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| 2. |
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| 3. |
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| 4. |
- Frumerie, Clara, et al.
(författare)
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Cooperative interactions between bacteriophage P2 integrase and its accessory factors IHF and Cox
- 2005
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Ingår i: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 332:1, s. 284-294
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Tidskriftsartikel (refereegranskat)abstract
- Bacteriophage P2 integrase (Int) mediates site-specific recombination leading to integration or excision of the phage genome in or out of the bacterial chromosome. Int belongs to the large family of tyrosine recombinases that have two different DNA recognition motifs binding to the arm and core sites, respectively, which are located within the phage attachment sites (attP). In addition to the P2 integrase, the accessory proteins Escherichia coli IHF and P2 Cox are needed for recombination. IHF is a structural protein needed for integration and excision by bending the DNA. As opposed to lambda, only one IHF site is found in P2 attP. P2 Cox controls the direction of recombination by inhibiting integration but being required for excision. In this work, the effects of accessory proteins on the capacity of Int to bind to its DNA recognition sequences are analyzed using electromobility shifts. P2 Int binds with low affinity to the arm site, and this binding is greatly enhanced by IHF. The arm binding domain of Int is located at the N-terminus. P2 Int binds with high affinity to the core site, and this binding is also enhanced by IHF. The fact that the cooperative binding of Int and IHF is strongly reduced by lengthening the distance between the IHF and core binding sites indicates that the distance between these sites may be important for cooperative binding. The Int and Cox proteins also bind cooperatively to attP.
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| 5. |
- Granberg, Fredrik, et al.
(författare)
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Adenovirus-induced alterations in host cell gene expression prior to the onset of viral gene expression
- 2006
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Ingår i: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 353:1, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- In this report, we have studied gene expression profiles in human primary lung fibroblasts (IMR-90) during the very early phase of an adenovirus infection. Eight out of twelve genes with known functions encoded transcription factors linked to two major cellular processes; inhibition of cell growth (ATF3, ATF4, KLF4, KLF6 and ELK3) and immune response (NR4A1 and CEBPB), indicating that the earliest consequences of an adenovirus infection are growth arrest and induction of an immune response. A time course analysis showed that the induction of these immediate-early response genes was transient and suppressed after the onset of the adenovirus early gene expression.
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| 6. |
- Grayson, Paul, et al.
(författare)
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The effect of genome length on ejection forces in bacteriophage lambda.
- 2006
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Ingår i: Virology. - : Elsevier BV. - 1096-0341 .- 0042-6822. ; 348:2, s. 430-436
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Tidskriftsartikel (refereegranskat)abstract
- A variety of viruses tightly pack their genetic material into protein capsids that are barely large enough to enclose the genome. In particular, in bacteriophages, forces as high as 60 pN are encountered during packaging and ejection, produced by DNA bending elasticity and self-interactions. The high forces are believed to be important for the ejection process, though the extent of their involvement is not yet clear. As a result, there is a need for quantitative models and experiments that reveal the nature of the forces relevant to DNA ejection. Here, we report measurements of the ejection forces for two different mutants of bacteriophage λ, λb221cI26 and λcI60, which differ in genome length by 30%. As expected for a force-driven ejection mechanism, the osmotic pressure at which DNA release is completely inhibited varies with the genome length: we find inhibition pressures of 15 atm and 25 atm, for the short and long genomes, respectively, values that are in agreement with our theoretical calculations.
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| 7. |
- Habjan, Matthias, et al.
(författare)
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Efficient production of Rift Valley fever virus-like particles : the antiviral protein MxA can inhibit primary transcription of bunyaviruses
- 2009
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Ingår i: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 385:2, s. 400-408
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Tidskriftsartikel (refereegranskat)abstract
- Rift Valley fever virus (RVFV) is a highly pathogenic member of the family Bunyaviridae that needs to be handled under biosafety level (BSL) 3 conditions. Here, we describe reverse genetics systems to measure RVFV polymerase activity in mammalian cells and to generate virus-like particles (VLPs). Recombinant polymerase (L) and nucleocapsid protein (N), expressed together with a minireplicon RNA, formed transcriptionally active nucleocapsids. These could be packaged into VLPs by additional expression of viral glycoproteins. The VLPs resembled authentic virus particles and were able to infect new cells. After infection, VLP-associated nucleocapsids autonomously performed primary transcription, and co-expression of L and N in VLP-infected cells allowed subsequent replication and secondary transcription. Bunyaviruses are potently inhibited by a human interferon-induced protein, MxA. However, the affected step in the infection cycle is not entirely characterized. Using the VLP system, we demonstrate that MxA inhibits both primary and secondary transcriptions of RVFV. A set of infection assays distinguishing between virus attachment, entry, and subsequent RNA synthesis confirmed that MxA is able to target immediate early RNA synthesis of incoming RVFV particles. Thus, our reverse genetics systems are useful for dissecting individual steps of RVFV infection under non-BSL3 conditions.
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| 8. |
- Harila, Kirsi, et al.
(författare)
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The Vpu-regulated endocytosis of HIV-1 Gag is clathrin-independent
- 2007
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Ingår i: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 369:2, s. 299-308
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Tidskriftsartikel (refereegranskat)abstract
- Recent results by us and others have shown that the accessory protein Vpu determines plasma membrane versus endosomal accumulation of the HIV-1 core protein Gag and progeny virions in the HeLa model of HIV-1 infection, since Vpu suppresses endocytosis of cell surface-associated Gag. In this report, we used pulse-chase studies and subcellular fractionations to investigate endocytosis of newly synthesized Gag in HeLa HI cells. The uptake of Gag in Delta Vpu-virus background was not blocked by inhibitors of clathrin-mediated endocytosis and macropinocytosis. The cholesterol-sequestering drug filipin inhibited the uptake, but only if the drug was applied before extensive multimerization of Gag had taken place. Thus, the uptake mechanism most likely is only indirectly dependent on cholesterol. Our results also indicated that targeting phenotype of Gag was different in confluent versus subconfluent cell cultures, which could perhaps explain some of the controversies in intracellular targeting of Gag. (c) 2007 Elsevier Inc. All rights reserved.
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| 9. |
- Hazard, Kristina, et al.
(författare)
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Human papillomavirus subtypes are not uncommon.
- 2007
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Ingår i: Virology. - : Elsevier BV. - 1096-0341 .- 0042-6822. ; 362:1, s. 6-9
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Tidskriftsartikel (refereegranskat)abstract
- While both variants and types of human papillomavirus (HPV) are common, subtypes (2-10% sequence divergence in the L1 gene) have been considered to be rare. We searched GenBank and in-house databases using a 440 nt L1 fragment and identified 7, 30 and 10 subtypes/putative subtypes in the HPV genera Alpha, Beta and Gamma, respectively. The number of types/putative types in each genus was 54, 58 and 103. Thus, there appears to exist at least 47 different subtypes/putative subtypes of HPV and they seem to be particularly common in the genus Betapapillomavirus.
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| 10. |
- Hultcrantz, Monica, et al.
(författare)
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Interferons induce an antiviral state in human pancreatic islet cells
- 2007
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Ingår i: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 367:1, s. 92-101
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Tidskriftsartikel (refereegranskat)abstract
- Enterovirus infections, in particular those with Coxsackieviruses, have been linked to the development of type 1 diabetes (T1D). Although animal models have demonstrated that interferons (IFNs) regulate virus-induced T1D by acting directly on the beta cell, little is known on the human pancreatic islet response to IFNs. Here we show that human islet cells respond to IFNs by expressing signature genes of antiviral defense. We also demonstrate that they express three intracellular sensors for viral RNA, the toll like receptor 3 (TLR3) gene, the retinoic acid-inducible gene I (RIG-I) and the melanoma differentiation-associated gene-5 (MDA-5), which induce type I IFN production in infected cells. Finally, we show for the first time that the IFN-induced antiviral state provides human islets with a powerful protection from the replication of Coxsackievirus. This may be critical for beta cell survival and protection from virus-induced T1D in humans.
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