Project description:Expression data from NIH-3T3 cells left uninfected or infected with MCMV for 2, 4 or 6h on total RNA as well as newly transcribed RNA labeled for 1-2, 3-4, and 5-6hpi. For newly transcribed RNA, the isolated RNA was labeled for 1h and separated from total cellular RNA following Trizol RNA preparation and thiol-specific biotinylation. We used microarrays to analyze the effects of MCMV infection in total and newly transcribed RNA. 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. NIH-3T3 cells (5th to 15th passage after thawing) were split from confluent plates 24h before start of the experiment. At the beginning of the experiment about 80% confluency was reached. The experiment was started by applying fresh, prewarmed, CO2-equilibrated medium containing either mock or MCMV particles (MOI 1). The MOI was increased by ~10-fold through centrifugal enhancement (2000g, 30min). Labeling was started 1, 3, or 5hpi after the end of centrifugal enhancement.

Project description:Expression data from NIH-3T3 cells left uninfected or infected with MCMV for 2, 4 or 6h on total RNA as well as newly transcribed RNA labeled for 1-2, 3-4, and 5-6hpi. For newly transcribed RNA, the isolated RNA was labeled for 1h and separated from total cellular RNA following Trizol RNA preparation and thiol-specific biotinylation. We used microarrays to analyze the effects of MCMV infection in total and newly transcribed RNA. 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.

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Newly transcribed RNA (nt-RNA) for IFN alpha and gamma time course

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