Flavivirus Capsid Proteins Facilitate Genome Compaction and Packaging
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA725703 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR14340800.fastq.gz | Fastqsanger.gz | |||
| SRR14340801.fastq.gz | Fastqsanger.gz | |||
| SRR14340802.fastq.gz | Fastqsanger.gz | |||
| SRR14340777.fastq.gz | Fastqsanger.gz | |||
| SRR14340778.fastq.gz | Fastqsanger.gz |
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Project description:Dengue virus (DENV) and Zika virus (ZIKV) are single-stranded (+)-sense RNA viruses that infect humans and mosquitoes, posing a significant health risk in tropical and subtropical regions. Mature virions are composed of an icosahedral shell of envelope (E) and membrane (M) proteins circumscribing a lipid bilayer, which in turn contains a complex of the approximately 11 kb genomic RNA with capsid (C) proteins. Whereas the structure of the envelope is clearly defined, the structure of the packaged genome in complex with C proteins remains elusive. Here, we investigate the interactions of C proteins with viral RNA, in solution and inside mature virions, via footprinting and cross-linking experiments. We demonstrate that C protein interactions with DENV and ZIKV genomes saturate at an RNA:C protein ratio below 1:250, and that binding site lengths on the genome exhibit a bimodal distribution, suggesting that RNA-C protein complexes occur in singlets or pairs. We show that interaction sites are preferentially sites with low base pairing, as measured by previously measured SHAPE reactivity indicating structuredness. We found no preference for specific sequence motifs or nucleotide composition. However, RNA-C protein binding sites are strongly associated with long-range RNA-RNA interaction sites, particularly inside virions. This helps to explain the need of C protein for viral genome packaging: the protein could coordinate those key interactions, promoting proper packing of viral RNA. Such sites are thus possible targets for drug development strategies against these and related viruses.
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Project description:Dengue virus (DENV) is a single-stranded (+)-sense RNA virus that infects humans and mosquitoes, posing a significant health risk in tropical and subtropical regions. Mature virions are composed of an icosahedral shell of envelope (E) and membrane (M) proteins circumscribing a lipid bilayer, which in turn contains a complex of the approximately 11 kb genomic RNA with capsid (C) proteins. Whereas the structure of the envelope is clearly defined, the structure of the packaged genome in complex with C proteins remains elusive. Here, we investigated the interactions of C proteins with viral RNA, in solution and inside mature virions, via footprinting and cross-linking experiments. We demonstrated that C protein interaction with DENV genomes saturates at an RNA:C protein ratio below 1:250. Moreover, we also showed that the length of the RNA genome interaction sites varies, in a multimodal distribution, consistent with the C protein binding to each RNA site mostly in singlets or pairs (and, in some instances, higher numbers). We showed that interaction sites are preferentially sites with low base pairing, as previously measured by 2'-acetylation analyzed by primer extension (SHAPE) reactivity indicating structuredness. We found a clear association pattern emerged: RNA-C protein binding sites are strongly associated with long-range RNA-RNA interaction sites, particularly inside virions. This, in turn, explains the need for C protein in viral genome packaging: the protein has a chief role in coordinating these key interactions, promoting proper packaging of viral RNA. Such sites are, thus, highly consequential for viral assembly, and, as such, may be targeted in future drug development strategies against these and related viruses.
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Project description:In this study, we describe a viral suppressor of RNA silencing encoded by the prototype flavivirus, yellow fever virus (YFV). We show that the YFV capsid protein inhibits RNA silencing in the mosquito Aedes aegypti by interfering with Dicer. These results suggest a molecular arms race between vector and pathogen underlies the continued existence of flaviviruses in nature.
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Project description:The recent outbreaks of Zika virus (ZIKV) and its association with birth defects known as Congenital Zika Syndrome warrant investigation on the molecular processes related to its infection and pathogenesis. Among the flavivirus family, only ZIKV is linked to microcephaly as announced by World Health Organization, suggesting uniqueness of ZIKV infection compared to other members. By analyzing the ZIKV-host interactome, we found that the key microRNA (miRNA) processing enzyme Dicer was a leading target of ZIKV capsid protein in neural stem cells (NSCs), and its deficiency facilitated ZIKV infection. Mechanistically, ZIKV capsid can directly interact with Dicer and block its ribonuclease activity, dampening the production of host miRNAs that are essential for neurogenesis. Interestingly, this capsid-mediated immune evasion is specific to ZIKV because capsid proteins from other close flaviviruses, e.g., dengue, yellow fever and West Nile viruses, cannot bind to Dicer or inhibit its function. By molecular mapping, we defined a ZIKV capsid H41R mutant with loss of interaction to Dicer and no longer affecting its activity. More importantly, ZIKV H41R mutant exerted almost no impact on neurogenesis in vitro when expressed in NSCs compared to wild type capsid, and in utero infection of recombinant ZIKV-H41R mutant virus resulted in less inhibition on corticogenesis than wild-type ZIKV in mouse embryos. Interestingly, the epidemic ZIKV strain reinforces the capsid-Dicer interaction by two amino acid substitution compared to ancient Africa strain. Thus, our study demonstrated that capsid-dependent suppression of Dicer function is a unique determinant of ZIKV immune evasion and pathogenesis, which may unveil a new mechanism for ZIKV-mediated microcephaly.
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Project description:Flavivirus, Zika virus Genome sequencing and assembly
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Project description:Cellular metabolism relies on the regulation and maintenance of mitochondrial DNA (mtDNA). Hundreds to thousands of copies of mtDNA exist in each cell, yet because mitochondria lack histones or other machinery important for nuclear genome compaction, it remains unresolved how mtDNA is packaged into individual nucleoids. In this study, we used long-read single-molecule accessibility mapping to measure the compaction of individual full-length mtDNA molecules at near single-nucleotide resolution. We found that, unlike the nuclear genome, human mtDNA largely undergoes all-or-none global compaction, with most nucleoids existing in an inaccessible, inactive state. Highly accessible mitochondrial nucleoids are co-occupied by transcription and replication components and selectively form a triple-stranded displacement loop structure. In addition, we showed that the primary nucleoid-associated protein TFAM directly modulates the fraction of inaccessible nucleoids both in vivo and in vitro, acting consistently with a nucleation-and-spreading mechanism to coat and compact mitochondrial nucleoids. Together, these findings reveal the primary architecture of mtDNA packaging and regulation in human cells.
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