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Properties of virion transactivator proteins encoded by primate cytomegaloviruses.

Nicholson IP, Sutherland JS, Chaudry TN, Blewett EL, Barry PA, Nicholl MJ, Preston CM - Virol. J. (2009)

Bottom Line: The results show that all UL82 homologs activate gene expression, and that neither host cell type nor promoter target sequence has major effects on these activities.In addition, significant differences were observed in the intranuclear localization of the UL82 homologs, and in their effects on Daxx.The results provide new information on early events in infection with cytomegaloviruses.

View Article: PubMed Central - HTML - PubMed

Affiliation: Medical Research Council Virology Unit, Church Street, Glasgow G115JR, UK. iain.nicholson@fishawack.com

ABSTRACT

Background: Human cytomegalovirus (HCMV) is a betaherpesvirus that causes severe disease in situations where the immune system is immature or compromised. HCMV immediate early (IE) gene expression is stimulated by the virion phosphoprotein pp71, encoded by open reading frame (ORF) UL82, and this transactivation activity is important for the efficient initiation of viral replication. It is currently recognized that pp71 acts to overcome cellular intrinsic defences that otherwise block viral IE gene expression, and that interactions of pp71 with the cell proteins Daxx and ATRX are important for this function. A further property of pp71 is the ability to enable prolonged gene expression from quiescent herpes simplex virus type 1 (HSV-1) genomes. Non-human primate cytomegaloviruses encode homologs of pp71, but there is currently no published information that addresses their effects on gene expression and modes of action.

Results: The UL82 homolog encoded by simian cytomegalovirus (SCMV), strain Colburn, was identified and cloned. This ORF, named S82, was cloned into an HSV-1 vector, as were those from baboon, rhesus monkey and chimpanzee cytomegaloviruses. The use of an HSV-1 vector enabled expression of the UL82 homologs in a range of cell types, and permitted investigation of their abilities to direct prolonged gene expression from quiescent genomes. The results show that all UL82 homologs activate gene expression, and that neither host cell type nor promoter target sequence has major effects on these activities. Surprisingly, the UL82 proteins specified by non-human primate cytomegaloviruses, unlike pp71, did not direct long term expression from quiescent HSV-1 genomes. In addition, significant differences were observed in the intranuclear localization of the UL82 homologs, and in their effects on Daxx. Strikingly, S82 mediated the release of Daxx from nuclear domain 10 substructures much more rapidly than pp71 or the other proteins tested. All UL82 homologs stimulated the early release of ATRX from nuclear domain 10.

Conclusion: All of the UL82 homolog proteins analysed activated gene expression, but surprising differences in other aspects of their properties were revealed. The results provide new information on early events in infection with cytomegaloviruses.

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Distribution patterns of UL82 homologs and ATRX. Monolayers of HFFF2 cells were infected with in1374 derivatives expressing YFP-tagged homologs and analysed by immunofluorescence at 3 h post infection at 38.5°C.
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Figure 5: Distribution patterns of UL82 homologs and ATRX. Monolayers of HFFF2 cells were infected with in1374 derivatives expressing YFP-tagged homologs and analysed by immunofluorescence at 3 h post infection at 38.5°C.

Mentions: It was reported previously that infection with in1316 resulted in the dispersal of ATRX at 3 h pi, a time at which YFPpp71 and Daxx remained at ND10 in a punctate distribution [21]. To investigate whether the UL82 homologs also promoted the early dispersal of ATRX, nuclei were examined at 3 h pi and 25 YFP positives scored for ATRX distribution. It was clear that expression of all UL82 homologs resulted in dispersal of ATRX even though the YFP signal was punctate (Fig. 5), and this was confirmed by quantification (Table 5). The homologs are therefore similar to pp71 in their abilities to promote the early dispersal of ATRX from ND10.


Properties of virion transactivator proteins encoded by primate cytomegaloviruses.

Nicholson IP, Sutherland JS, Chaudry TN, Blewett EL, Barry PA, Nicholl MJ, Preston CM - Virol. J. (2009)

Distribution patterns of UL82 homologs and ATRX. Monolayers of HFFF2 cells were infected with in1374 derivatives expressing YFP-tagged homologs and analysed by immunofluorescence at 3 h post infection at 38.5°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2693105&req=5

Figure 5: Distribution patterns of UL82 homologs and ATRX. Monolayers of HFFF2 cells were infected with in1374 derivatives expressing YFP-tagged homologs and analysed by immunofluorescence at 3 h post infection at 38.5°C.
Mentions: It was reported previously that infection with in1316 resulted in the dispersal of ATRX at 3 h pi, a time at which YFPpp71 and Daxx remained at ND10 in a punctate distribution [21]. To investigate whether the UL82 homologs also promoted the early dispersal of ATRX, nuclei were examined at 3 h pi and 25 YFP positives scored for ATRX distribution. It was clear that expression of all UL82 homologs resulted in dispersal of ATRX even though the YFP signal was punctate (Fig. 5), and this was confirmed by quantification (Table 5). The homologs are therefore similar to pp71 in their abilities to promote the early dispersal of ATRX from ND10.

Bottom Line: The results show that all UL82 homologs activate gene expression, and that neither host cell type nor promoter target sequence has major effects on these activities.In addition, significant differences were observed in the intranuclear localization of the UL82 homologs, and in their effects on Daxx.The results provide new information on early events in infection with cytomegaloviruses.

View Article: PubMed Central - HTML - PubMed

Affiliation: Medical Research Council Virology Unit, Church Street, Glasgow G115JR, UK. iain.nicholson@fishawack.com

ABSTRACT

Background: Human cytomegalovirus (HCMV) is a betaherpesvirus that causes severe disease in situations where the immune system is immature or compromised. HCMV immediate early (IE) gene expression is stimulated by the virion phosphoprotein pp71, encoded by open reading frame (ORF) UL82, and this transactivation activity is important for the efficient initiation of viral replication. It is currently recognized that pp71 acts to overcome cellular intrinsic defences that otherwise block viral IE gene expression, and that interactions of pp71 with the cell proteins Daxx and ATRX are important for this function. A further property of pp71 is the ability to enable prolonged gene expression from quiescent herpes simplex virus type 1 (HSV-1) genomes. Non-human primate cytomegaloviruses encode homologs of pp71, but there is currently no published information that addresses their effects on gene expression and modes of action.

Results: The UL82 homolog encoded by simian cytomegalovirus (SCMV), strain Colburn, was identified and cloned. This ORF, named S82, was cloned into an HSV-1 vector, as were those from baboon, rhesus monkey and chimpanzee cytomegaloviruses. The use of an HSV-1 vector enabled expression of the UL82 homologs in a range of cell types, and permitted investigation of their abilities to direct prolonged gene expression from quiescent genomes. The results show that all UL82 homologs activate gene expression, and that neither host cell type nor promoter target sequence has major effects on these activities. Surprisingly, the UL82 proteins specified by non-human primate cytomegaloviruses, unlike pp71, did not direct long term expression from quiescent HSV-1 genomes. In addition, significant differences were observed in the intranuclear localization of the UL82 homologs, and in their effects on Daxx. Strikingly, S82 mediated the release of Daxx from nuclear domain 10 substructures much more rapidly than pp71 or the other proteins tested. All UL82 homologs stimulated the early release of ATRX from nuclear domain 10.

Conclusion: All of the UL82 homolog proteins analysed activated gene expression, but surprising differences in other aspects of their properties were revealed. The results provide new information on early events in infection with cytomegaloviruses.

Show MeSH
Related in: MedlinePlus