A phage nucleus-associated RNA-binding protein is required for jumbo phage infection
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Abstract
Large-genome bacteriophages (jumbo phages) of the proposed family Chimalliviridae assemble a nucleus-like compartment bounded by a protein shell that protects the replicating phage genome from host-encoded restriction enzymes and DNA-targeting CRISPR-Cas nucleases. While the nuclear shell provides broad protection against host nucleases, it necessitates transport of mRNA out of the nucleus-like compartment for translation by host ribosomes, and transport of specific proteins into the nucleus-like compartment to support DNA replication and mRNA transcription. Here, we identify a conserved phage nuclear shell-associated protein that we term Chimallin C (ChmC), which adopts a nucleic acid-binding fold, binds RNA with high affinity in vitro, and binds phage mRNAs in infected cells. ChmC also forms phase-separated condensates with RNA in vitro. Targeted knockdown of ChmC using mRNA-targeting dCas13d results in accumulation of phage-encoded mRNAs in the phage nucleus, reduces phage protein production, and compromises virion assembly. Taken together, our data show that the conserved ChmC protein plays crucial roles in the viral life cycle, potentially by facilitating phage mRNA translocation through the nuclear shell to promote protein production and virion development.
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Our work reveals the first identified RNA binding protein necessary for bacteriophage replication, with potential roles in mRNA production, export, and translation to support the unique life cycle of nucleus-forming jumbo phages
Such a great paper! Impressive combination of approaches to reveal exciting new biology! Congrats!
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ChmC preferentially associates with phage mRNAs compared to host mRNAs
Is this conclusion complicated by the fact that the host genome has been degraded and thus there is likely to be much more phage mRNA present in the cell at the timepoint analyzed?
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non-conserved genes are colored white
Seems like there aren't any of these shown in this figure?
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located in a highly conserved cluster of genes
It would be great to know more about how well-conserved this cluster is! Might be nice to show some genomic alignments, or some info about the extent of conservation across jumbo phage.
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