Unknown,Transcriptomics,Genomics,Proteomics

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Murine Cytomegalovirus Protein pM79 is a Key Regulator for Viral Late Transcription

ABSTRACT: We characterized the role of the conserved murine cytomegalovirus (MCMV) gene M79. Using a recombinant MCMV virus carrying a tagged M79 coding sequence, we showed that M79 encoded a protein (pM79) which was expressed at late times of infection and localized to nuclear viral replication compartments. M79 transcription was largely dependent on viral DNA synthesis but was markedly stimulated by pM79, suggesting a positive feedback loop. To investigate its role, we created the recombinant virus SMin79, in which the M79 coding sequence was disrupted by an 88-nt insertion. We subsequently repaired the mutation to generate marker-rescued virus SMrev79. While SMrev79 grew efficiently in fibroblasts, SMin79 failed to produce infectious progeny but was rescued by pM79 expression in trans. During SMin79 infection, representative viral immediate early and early gene products, as well as viral DNA, accumulated efficiently. Formation of viral replication compartments also appeared normal. Pulsed field gel electrophoresis analysis indicated that the overall structure of replicating viral DNA was indistinguishable in cells infected with SMin79 compared to that with wild type virus. However, the accumulation of viral products for late gene M55 was severely compromised. Viral oligonucleotide tiled array analysis revealed that the accumulation of many late transcripts, defined by their sensitivity to viral DNA synthesis inhibitor phosphonoacetic acid, was markedly reduced by pM79 mutation. This study extends our previous work to suggest that cytomegaloviruses use a conserved mechanism to promote transcription at late stages of infection, and that pM79 regulates expression of a subset of viral DNA synthesis-dependent transcripts. This study consists of 4 unreplicated samples. RNA from Mock-infected, WT infected, WT infected in the presence of PAA, and a mutant M79 version of MCMV.

ORGANISM(S): Mus musculus

SUBMITTER: travis Chapa

PROVIDER: E-GEOD-47586 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:During viral infections cellular gene expression is subject to rapid alterations induced by both viral and antiviral mechanisms. In this study, we applied metabolic labeling of newly transcribed RNA with 4-thiouridine (4sU-tagging) to dissect the real-time kinetics of cellular and viral transcriptional activity during lytic murine cytomegalovirus (MCMV) infection. Microarray profiling on newly transcribed RNA obtained from different times during the first six hours of MCMV infection revealed discrete functional networks of cellular genes regulated with distinct kinetics at surprising temporal resolution. Most of these were undetectable in total RNA, either due to low temporal sensitivity of standard gene expression profiling using total RNA, or due to rapid (viral) counter-regulation. Furthermore, metabolic labeling and purification of newly transcribed RNA detailed the real-time kinetics and regulation of viral gene expression in absence of any interfering virion-associated RNA. Both qRT-PCR and next-generation sequencing of newly transcribed RNA demonstrated an unexpected peak of viral gene expression during the first two hours of infection including transcription of immediate early, early and even well characterized late genes. Interestingly, this peak was subject to rapid gene silencing (independent of the multiplicity of infection) with similar transcriptional activity only reached late in infection. For some genes, e.g. m152, this resulted in massive down-regulation of transcriptional activity by 6 hours post infection, which was not even reversed late in infection. Our findings thus highlight the importance of transcriptional activity during the first few hours of CMV infection and hint at novel mechanisms governing the kinetics of viral gene expression. In conclusion, studying real-time transcriptional activity during lytic CMV infection provides intriguing new insights into the regulation of cellular and viral gene expression. In total 13 samples were examined: 3 samples of total RNA (mock, 25, 48 hours past MCMV infection), 3 samples pre-existing RNA (mock, 25, 48 hpi), and 7 samples newly-transcribed RNA (mock, 1-2, 5-6, 11-12, 18-19, 24-25, 47-48 hpi)

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Murine Cytomegalovirus Protein pM79 is a Key Regulator for Viral Late Transcription

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