Project description:Heldt2012 - Influenza Virus Replication The model describes the life cycle of influenza A virus in a mammalian cell including the following steps: attachment of parental virions to the cell membrane, receptor-mediated endocytosis, fusion of the virus envelope with the endosomal membrane, nuclear import of vRNPs, viral transcription and replication, translation of the structural viral proteins, nuclear export of progeny vRNPs and budding of new virions. It also explicitly accounts for the stabilization of cRNA by viral polymerases and NP and the inhibition of vRNP activity by M1 protein binding. In short, the model focuses on the molecular mechanism that controls viral transcription and replication. This model is described in the article: Modeling the intracellular dynamics of influenza virus replication to understand the control of viral RNA synthesis. Heldt FS, Frensing T, Reichl U. J Virol. Abstract: Influenza viruses transcribe and replicate their negative-sense RNA genome inside the nucleus of host cells via three viral RNA species. In the course of an infection, these RNAs show distinct dynamics, suggesting that differential regulation takes place. To investigate this regulation in a systematic way, we developed a mathematical model of influenza virus infection at the level of a single mammalian cell. It accounts for key steps of the viral life cycle, from virus entry to progeny virion release, while focusing in particular on the molecular mechanisms that control viral transcription and replication. We therefore explicitly consider the nuclear export of viral genome copies (vRNPs) and a recent hypothesis proposing that replicative intermediates (cRNA) are stabilized by the viral polymerase complex and the nucleoprotein (NP). Together, both mechanisms allow the model to capture a variety of published data sets at an unprecedented level of detail. Our findings provide theoretical support for an early regulation of replication by cRNA stabilization. However, they also suggest that the matrix protein 1 (M1) controls viral RNA levels in the late phase of infection as part of its role during the nuclear export of viral genome copies. Moreover, simulations show an accumulation of viral proteins and RNA toward the end of infection, indicating that transport processes or budding limits virion release. Thus, our mathematical model provides an ideal platform for a systematic and quantitative evaluation of influenza virus replication and its complex regulation. With the current parameter set, the model reproduces an infection at a multiplicity of infection (MOI) of 10. Figure 2A of the paper is reproduced here, with parameters kDegRnp and kSynP changed to zeros. Initial conditions and parameter changes that were used to obtain specific figures in the article can be found in Table A2. The model has the correct value for kAttLo as 4.55e-04. The value of this parameter mentioned as 4.55e-02 in Table 1 of the paper is incorrect. This is checked with the author. This model is hosted on BioModels Database and identified by: MODEL1307270000 . To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models . To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:The protein arginine methyl transferase PRMT5 is an enzyme expressed in oligodendrocyte lineage cells and responsible for the symmetric methylation of arginine residues on histone tails. Previous work from our laboratory identified PRMT5 as critical for myelination, due to its transcriptional regulation of survival and early stages of differentiation. However, besides its nuclear localization, PRMT5 is found at high levels in the cytoplasm of oligodendrocyte progenitor cells (OPCs) and yet, its interacting partners and non-histone substrates in this lineage, remain elusive. By using mass spectrometry on protein eluates from extracts generated from OPC and immunoprecipitated with PRMT5 antibodies, we identified 1116 proteins as PRMT5 interacting partners. These proteins are related to molecular functions such as RNA binding, ribosomal structure, nucleotide binding, cadherin and actin binding, GTP and GTPase activity. We then investigated PRMT5 substrates using iTRAQ-based proteomics on protein samples isolated from CRISPR-PRMT5 knockdown immortalized oligodendrocyte progenitors compared to CRISPR-EGFP controls. This analysis identified 169 peptides with statistically different symmetric methylation of arginine residues in the two groups. Those peptides led to 30 unique non-histone substrates of PRMT5. The majority of these proteins were consistent with PRMT5 substrates, previously identified in distinct cancer cell lines (e.g. the transcription factor ZN326), and were functionally related to RNA processing and transport, splicing, regulation of mRNA stability and transcription. In addition, we detected three substrates as unique to the oligodendrocyte lineage and not identified in cancer cells. They included the proline-rich protein PRC2C, involved in methyl-RNA binding, the RNA binding protein KHDR2, regulating splicing events and the heterogeneous nuclear RNA binding protein HNRPD, involved in regulation of RNA stability. Together, these results highlight a cell-specific role of PRMT5 in regulating, not only transcription, but RNA processing and translation in OPCs. (287 WORDS)

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