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UL49 is an essential subunit of the viral pre-initiation complex that regulates human cytomegalovirus gene transcription.

ABSTRACT: More than half the world's population is infected with human cytomegalovirus (HCMV), causing congenital birth defects and impacting the immuno-compromised. Many of the >170 HCMV genes remain uncharacterized, and this gap in knowledge limits the development of novel antivirals. In this study, we investigated the essential viral protein UL49 and found it displayed leaky late expression kinetics, and localized to nuclear replication compartments. Cells infected with mutant UL49 virus were unable to produce infectious virions and phenocopied other beta-gamma viral pre-initiation complex (vPIC) subunit (UL79, UL87, UL91, UL92, and UL95) mutant infections. RNA-seq analysis of vPIC mutant infections revealed a consistent diminution of genes encoding capsid subunits, including TRX2/UL85 and MCP/UL86, envelope glycoproteins gM, gL and gO, and egress-associated tegument proteins UL99 and UL103. Therefore, as a member of the vPIC, UL49 serves as a fundamental HCMV effector that governs viral gene transcription required to complete the replication cycle.

SUBMITTER: Turner DL

PROVIDER: S-EPMC9530030 | biostudies-literature | 2022 Oct

REPOSITORIES: biostudies-literature

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UL49 is an essential subunit of the viral pre-initiation complex that regulates human cytomegalovirus gene transcription.

Turner Declan L DL Fritzlar Svenja S Sadeghipour Sara S Barugahare Adele A AA Russ Brendan E BE Turner Stephen J SJ Mathias Rommel A RA

iScience 20220919 10

More than half the world's population is infected with human cytomegalovirus (HCMV), causing congenital birth defects and impacting the immuno-compromised. Many of the >170 HCMV genes remain uncharacterized, and this gap in knowledge limits the development of novel antivirals. In this study, we investigated the essential viral protein UL49 and found it displayed leaky late expression kinetics, and localized to nuclear replication compartments. Cells infected with mutant UL49 virus were unable to ...[more]

PMID: 36204275

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Project description:BACKGROUND:Human cytomegalovirus (HCMV) can be managed by monitoring HCMV DNA in the blood and giving valganciclovir when viral load exceeds a defined value. We hypothesised that such pre-emptive therapy should occur earlier than the standard 3000 genomes/ml (2520 IU/ml) when a seropositive donor transmitted virus to a seronegative recipient (D+R-) following solid organ transplantation (SOT). METHODS:Our local protocol was changed so that D+R- SOT patients commenced valganciclovir once the viral load exceeded 200 genomes/ml; 168 IU/ml (new protocol). The decision point remained at 3000 genomes/ml (old protocol) for the other two patient subgroups (D+R+, D-R+). Virological outcomes were assessed three years later, when 74 D+R- patients treated under the old protocol could be compared with 67 treated afterwards. The primary outcomes were changes in peak viral load, duration of viraemia and duration of treatment in the D+R- group. The secondary outcome was the proportion of D+R- patients who developed subsequent viraemia episodes. FINDINGS:In the D+R- patients, the median values of peak viral load (30,774 to 11,135 genomes/ml, p<0.0215) were significantly reduced on the new protocol compared to the old, but the duration of viraemia and duration of treatment were not. Early treatment increased subsequent episodes of viraemia from 33/58 (57%) to 36/49 (73%) of patients (p< 0.0743) with a significant increase (p = 0.0072) in those episodes that required treatment (16/58; 27% versus 26/49; 53%). Median peak viral load increased significantly (2,103 to 3,934 genomes/ml, p<0.0249) in the D+R+ but not in the D-R+ patient subgroups. There was no change in duration of viraemia or duration of treatment for any patient subgroup. INTERPRETATION:Pre-emptive therapy initiated at the first sign of viraemia post-transplant significantly reduced the peak viral load but increased later episodes of viraemia, consistent with the hypothesis of reduced antigenic stimulation of the immune system.

Project description:Human cytomegalovirus (HCMV) is a common cause of morbidity and mortality in immunocompromised and immunosuppressed individuals. During infection, HCMV is known to employ host transcription factors to facilitate viral gene expression. To further understand the previously observed delayed viral replication and protein expression in p53 knockout cells, we conducted microarray analyses on p53+/+ and p53-/- immortalized fibroblast cell lines. At 12 hpi, applying the significance criteria defined above, no genes showed a significant difference in any of the comparisons. At 24 hpi, we found 19 genes to be significantly different in the THF versus p53-/- comparison and 14 genes to be significantly different in the HFF versus p53-/- comparison. Eleven genes were shared between HFF and THF cells when compared to p53-/- cells (UL30, UL54, UL63, UL65, UL69, UL75, UL110, UL122, IRL4, IRS1, TRS1, shown in bold in Table 1). Eight genes were unique in the THF versus p53-/- comparison (UL48, UL68, UL84, UL100, UL106, UL109, UL111, RL5A), and three genes in the HFF versus p53-/- cell comparison (UL14, UL16, US2). When comparing HFF and THF cells, only US2 showed a significant difference. The ratio (HFF versus p53-/- divided by THF versus p53-/-) of the expression levels of the eleven shared genes from the HFF versus p53-/- and THF versus p53-/- comparisons was an averaged 1.2, indicating that, with the exception of US2, these two cell lines behaved similarly with respect to p53-driven viral gene expression. Keywords: time course, virus, cytomegalo, hhv5, infection, p53 Each slide consisted of 4 arrays. Each array consisted of 305 control features, 1265 cellular gene features and 670 viral gene features. The study was performed on 6 slides (HFF-THF, HFF-p53-/-, THF-p53-/- at 12 and 24 hpi). 3 arrays per slide were hybridized with 3 biological replicates of labelled RNA, the 4th array was hybridized with an equimolar mixture of the 3 biological replicate samples. This array was used for control purposes only, and the results were not used for downstream calculations. Each slide was stripped and reprobed two times to provide 3 technical replicates of each sample. As our experiments concentrated on viral genes and their expression, cellular genes were not further analyzed in this study.

Project description:Development of a cytomegalovirus (CMV) vaccine is a major public health priority due to the risk of congenital infection. A key component of a vaccine is thought to be an effective neutralizing antibody response against the viral glycoproteins necessary for cell entry. Species specificity of human CMV (HCMV) precludes direct studies in an animal model. The guinea pig is the only small animal model for congenital cytomegalovirus infection. Analysis of the guinea pig CMV (GPCMV) genome indicates that it potentially encodes homologs to the HCMV glycoproteins (including gB, gH, gL, gM, gN and gO) that form various cell entry complexes on the outside of the virus: gCI (gB); gCII (gH/gL/gO); gCIII (gM/gN). The gB homolog (GP55) has been investigated as a candidate subunit vaccine but little is known about the other homolog proteins. GPCMV glycoproteins were investigated by transient expression studies which indicated that homolog glycoproteins to gN and gM, or gH, gL and gO were able to co-localize in cells and generate respective homolog complexes which could be verified by immunoprecipitation assays. ELISA studies demonstrated that the individual complexes were highly immunogenic in guinea pigs. The gO (GP74) homolog protein has 13 conserved N-glycosylation sites found in HCMV gO. In transient expression studies, only the glycosylated protein is detected but in virus infected cells both N-glycosylated and non-glycosylated gO protein were detected. In protein interaction studies, a mutant gO that lacked N-glycosylation sites had no impact on the ability of the protein to interact with gH/gL which indicated a potential alternative function associated with these sites. Knockout GPCMV BAC mutagenesis of the respective glycoprotein genes (GP55 for gB, GP75 for gH, GP115 for gL, GP100 for gM, GP73 for gN and GP74 for gO) in separate reactions was lethal for virus regeneration on fibroblast cells which demonstrated the essential nature of the GPCMV glycoproteins. The gene knockout results were similar to HCMV, except in the case of the gO homolog, which was non-essential in epithelial tropic virus but essential in lab adapted GPCMV. Overall, the findings demonstrate the similarity between HCMV and GPCMV glycoproteins and strengthen the relevance of this model for development of CMV intervention strategies.

Dataset Information

UL49 is an essential subunit of the viral pre-initiation complex that regulates human cytomegalovirus gene transcription.

Publications

UL49 is an essential subunit of the viral pre-initiation complex that regulates human cytomegalovirus gene transcription.

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