Similar Datasets
Project description:Herpes simplex virus 1 (HSV-1) transcription is tightly regulated in a temporal cascade, utilizing cellular RNA polymerase (Pol). We previously observed that infection with HSV-1 mutants lacking immediate early (IE) genes a0, a4 and a22 exhibited unusually high levels of aberrant transcription across the viral genome at just 1.5 hpi. The strongest effect occurred in the absence of a4, which is both an essential transcriptional activator and repressor. The goal of the current study was to define the mechanism of ICP4-mediated early transcriptional repression on the viral genome. Using the transcriptomic tools PRO-Cap, PRO-Seq, GRO-Seq and Nanopore direct RNA sequencing we found that initiation was elevated at viral promoters of all temporal classes in the absence of ICP4. Despite higher levels of initiation, transcription of non-IE genes was stalled within gene bodies and did not lead to production of mature mRNA. We therefore posit that HSV-1 retains additional ICP4-independent mechanisms to limit expression of viral genes that initiate prematurely. The data also indicated rapid release from promoter proximal pausing and progression along HSV IE genes and revealed termination as an important rate -limiting regulatory step. These findings highlight multiple mechanisms that HSV-1 employs to regulate early transcription and identify ICP4’s repressive role is to restrict initiation on non IE genes, thereby ensuring correct progression of the temporal cascade.
2023-09-05 | GSE235872 | GEO
Project description:Herpes simplex virus 1 (HSV-1) transcription is tightly regulated in a temporal cascade, utilizing cellular RNA polymerase (Pol). We previously observed that infection with HSV-1 mutants lacking immediate early (IE) genes a0, a4 and a22 exhibited unusually high levels of aberrant transcription across the viral genome at just 1.5 hpi. The strongest effect occurred in the absence of a4, which is both an essential transcriptional activator and repressor. The goal of the current study was to define the mechanism of ICP4-mediated early transcriptional repression on the viral genome. Using the transcriptomic tools PRO-Cap, PRO-Seq, GRO-Seq and Nanopore direct RNA sequencing we found that initiation was elevated at viral promoters of all temporal classes in the absence of ICP4. Despite higher levels of initiation, transcription of non-IE genes was stalled within gene bodies and did not lead to production of mature mRNA. We therefore posit that HSV-1 retains additional ICP4-independent mechanisms to limit expression of viral genes that initiate prematurely. The data also indicated rapid release from promoter proximal pausing and progression along HSV IE genes and revealed termination as an important rate -limiting regulatory step. These findings highlight multiple mechanisms that HSV-1 employs to regulate early transcription and identify ICP4’s repressive role is to restrict initiation on non IE genes, thereby ensuring correct progression of the temporal cascade.
2023-09-05 | GSE235227 | GEO
Project description:Herpes simplex virus 1 (HSV-1) transcription is tightly regulated in a temporal cascade, utilizing cellular RNA polymerase (Pol). We previously observed that infection with HSV-1 mutants lacking immediate early (IE) genes a0, a4 and a22 exhibited unusually high levels of aberrant transcription across the viral genome at just 1.5 hpi. The strongest effect occurred in the absence of a4, which is both an essential transcriptional activator and repressor. The goal of the current study was to define the mechanism of ICP4-mediated early transcriptional repression on the viral genome. Using the transcriptomic tools PRO-Cap, PRO-Seq, GRO-Seq and Nanopore direct RNA sequencing we found that initiation was elevated at viral promoters of all temporal classes in the absence of ICP4. Despite higher levels of initiation, transcription of non-IE genes was stalled within gene bodies and did not lead to production of mature mRNA. We therefore posit that HSV-1 retains additional ICP4-independent mechanisms to limit expression of viral genes that initiate prematurely. The data also indicated rapid release from promoter proximal pausing and progression along HSV IE genes and revealed termination as an important rate -limiting regulatory step. These findings highlight multiple mechanisms that HSV-1 employs to regulate early transcription and identify ICP4’s repressive role is to restrict initiation on non IE genes, thereby ensuring correct progression of the temporal cascade.
2023-09-05 | GSE235226 | GEO
Project description:Herpes simplex virus 1 (HSV-1) transcription is tightly regulated in a temporal cascade, utilizing cellular RNA polymerase (Pol). We previously observed that infection with HSV-1 mutants lacking immediate early (IE) genes a0, a4 and a22 exhibited unusually high levels of aberrant transcription across the viral genome at just 1.5 hpi. The strongest effect occurred in the absence of a4, which is both an essential transcriptional activator and repressor. The goal of the current study was to define the mechanism of ICP4-mediated early transcriptional repression on the viral genome. Using the transcriptomic tools PRO-Cap, PRO-Seq, GRO-Seq and Nanopore direct RNA sequencing we found that initiation was elevated at viral promoters of all temporal classes in the absence of ICP4. Despite higher levels of initiation, transcription of non-IE genes was stalled within gene bodies and did not lead to production of mature mRNA. We therefore posit that HSV-1 retains additional ICP4-independent mechanisms to limit expression of viral genes that initiate prematurely. The data also indicated rapid release from promoter proximal pausing and progression along HSV IE genes and revealed termination as an important rate -limiting regulatory step. These findings highlight multiple mechanisms that HSV-1 employs to regulate early transcription and identify ICP4’s repressive role is to restrict initiation on non IE genes, thereby ensuring correct progression of the temporal cascade.
2023-09-05 | GSE235224 | GEO
Project description:Herpes Simplex Virus Type-1 (HSV-1) forms progeny in the nucleus within distinct membrane-less inclusions, the viral replication compartments (VRCs), where viral gene expression, DNA replication, and packaging occur. The way in which the VRCs maintain spatial integrity remains unresolved. Here, we demonstrate that the essential viral transcription factor ICP4 is an intrinsically disordered protein (IDP) capable of driving protein condensation and liquid-liquid phase separation (LLPS) in transfected cells. Particularly, ICP4 forms nuclear liquid-like condensates in a dose- and time-dependent manner. Fluorescence recovery after photobleaching (FRAP) assays revealed rapid exchange rates of EYFP-ICP4 between phase-separated condensates and the surroundings, akin to other viral IDPs that drive LLPS. Likewise, HSV-1 VRCs revealed by EYFP-tagged ICP4 retained their liquid-like nature, suggesting that they are phase-separated condensates. Individual VRCs homotypically fused when reaching close proximity and grew over the course of infection. Together, the results of this study demonstrate that the HSV-1 transcription factor ICP4 has characteristics of a viral IDP, forms condensates in the cell nucleus by LLPS, and can be used as a proxy for HSV-1 VRCs with characteristics of liquid-liquid phase-separated condensates.
| S-EPMC8123221 | biostudies-literature
Project description:Hepes simplex Virus type 1 (HSV-1) is an enveloped DNA virus that can cause lytic and latent infection. miRNAs post-transcriptionally regulate gene expression, and our previous work has indicated that HSV-1 infection induces miR-101 expression in HeLa cells. The present study demonstrates that HSV-1-induced miR-101 is mainly derived from its precursor hsa-mir-101-2, and the HSV-1 immediate early gene ICP4 (infected-cell polypeptide 4) directly binds to the hsa-mir-101-2 promoter to activate its expression. RNA-binding protein G-rich sequence factor 1 (GRSF1) was identified as a new target of miR-101; GRSF1 binds to HSV-1 p40 mRNA and enhances its expression, facilitating viral proliferation. Together, ICP4 induces miR-101 expression, which downregulates GRSF1 expression and attenuates the replication of HSV-1. This allows host cells to maintain a permissive environment for viral replication by preventing lytic cell death. These findings indicate that HSV-1 early gene expression modulates host miRNAs to regulate molecular defense mechanisms. This study provides novel insight into host-virus interactions in HSV-1 infection and may contribute to the development of antiviral therapeutics.
| S-EPMC4794718 | biostudies-literature
Project description:VP22 is a major tegument protein of equine herpesvirus type 1 (EHV-1). In the present study, we examined functions of VP22 in EHV-1 replication by viral protein expression analyses in cells infected with the VP22-deficient virus. The expressions of several viral proteins in the cells infected with the VP22-deficient virus were lower than those in the cells infected with the parent virus. One of the weakly expressed proteins was identified as ICP4, which is a major regulatory protein encoded by an immediate early gene of EHV-1. A real-time PCR analysis showed that the mRNA expression of ICP4 was the same in cells infected with the parent and VP22-deficient viruses. Hence, VP22 appears to promote synthesis of ICP4 post-transcriptionally.
| S-EPMC5836769 | biostudies-literature
Project description:The molecular mechanisms mediating herpes simplex virus type 1 (HSV-1) gene silencing during latent infection are not clear. Five copies of early growth response gene 1 (Egr-1) binding elements were identified in the intron of HSV-1 ICP22 (infected cell protein No. 22) gene, leading to the hypothesis that Egr-1 binds to the viral genome and regulates the viral gene expression. Transient co-transfection assays indicated that Egr-1 negatively regulated the transcription of both full-length and intron-removed ICP22 promoters. The same assays also revealed that Egr-1 repressed ICP4 (infected cell protein No. 4) promoter activity in a dose-dependent manner but showed less inhibition when the intron was removed. Histone deacetylation was not involved in this regulation since histone deacetylase inhibitor trichostatin A did not exhibit any effect on Egr-1-mediated repression. Chromatin immunoprecipitation assays showed that Egr-1 reduced the binding of Sp1 to the promoters and that the co-repressor Nab2 (NGFI-A/EGR1-binding protein) was recruited to the proximity of ICP4 in the presence of Egr-1. These results suggested that the multifunctional transcription factor Egr-1 can repress HSV-1 immediate-early gene expression through the recruitment of co-repressor Nab2 and reduction of Sp1 occupancy, and thus may play a critical role in HSV-1 gene silencing during latency.
| S-EPMC7092374 | biostudies-literature
Project description:G-quadruplexes (G4s) are four-stranded nucleic acid structures abundant at gene promoters. They can adopt several distinctive conformations. G4s have been shown to form in the herpes simplex virus-1 (HSV-1) genome during its viral cycle. Here by cross-linking/pull-down assay we identified ICP4, the major HSV-1 transcription factor, as the protein that most efficiently interacts with viral G4s during infection. ICP4 specific and direct binding and unfolding of parallel G4s, including those present in HSV-1 immediate early gene promoters, induced transcription in vitro and in infected cells. This mechanism was also exploited by ICP4 to promote its own transcription. Proximity ligation assay allowed visualization of G4-protein interaction at the single selected G4 in cells. G4 ligands inhibited ICP4 binding to G4s. Our results indicate the existence of a well-defined G4-viral protein network that regulates the productive HSV-1 cycle. They also point to G4s as elements that recruit transcription factors to activate transcription in cells.
| S-EPMC8087788 | biostudies-literature
Project description:During primary infection of its human host, Herpes Simplex Virus Type-1 (HSV-1) establishes latency in neurons where the viral genome is maintained in a circular form associated with nucleosomes in a chromatin configration. During latency, most viral genes are silenced, although the molecular mechanisms responsible for this are unclear. We hypothesized that neuronal factors repress HSV-1 gene expression during latency. A search of the HSV-1 DNA sequence for potential regulatory elements identified a Repressor Element-1/Neuronal Restrictive Silencer Element (RE-1/NRSE) located between HSV-1 genes ICP22 and ICP4. We predicted that the Repressor Element Silencing Transcription Factor/Neuronal Restrictive Silencer Factor (REST/NRSF) regulates expression of ICP22 and ICP4.Transient cotransfection indicated that REST/NRSF inhibited the activity of both promoters. In contrast, cotransfection of a mutant form of REST/NRSF encoding only the DNA-binding domain of the protein resulted in less inhibition. Stably transformed cell lines containing episomal reporter plasmids with a chromatin structure showed that REST/NRSF specifically inhibited the ICP4 promoter, but not the ICP22 promoter. REST/NRSF inhibition of the ICP4 promoter was reversed by histone deacetylase (HDAC) inhibitor Trichostatin A (TSA). Additionally, chromatin immuno-precipitation (ChIP) assays indicated that the corepressor CoREST was recruited to the proximity of ICP4 promoter and that acetylation of histone H4 was reduced in the presence of REST/NRSF.Since the ICP4 protein is a key transactivator of HSV-1 lytic cycle genes, these results suggest that REST/NRSF may have an important role in the establishment and/or maintenance of HSV-1 gene silencing during latency by targeting ICP4 expression.
| S-EPMC1906746 | biostudies-literature