biostudies-literatureEnustun EAmerican Heart AssociationU.S. Department of EnergyHoward Hughes Medical Institute Emerging Pathogens InitiativeHoward Hughes Medical InstituteBiological and Environmental ResearchNational Institutes of HealthNIH HHSNIGMS NIH HHS4440-4455https://www.ebi.ac.uk/biostudies/studies/S-EPMC11077065biostudies-literatureUnknown52(8)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 fNucleic acids researchA phage nucleus-associated RNA-binding protein is required for jumbo phage infection.PMC11077065DE-AC02-05CH11231S10 OD021724R01 HG004659R01 GM129245R35 GM144121Doudna JAAdler BAGu YDeep ACleveland DWBintu BEnustun EArmbruster EGLee JChaikeeratisak VGhassemian MZhang SYeo GWNaritomi JTCorbett KDAigner SPogliano JCress BFYee BAMalukhina KLiang QfalseA phage nucleus-associated RNA-binding protein is required for jumbo phage infection.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 f2024-01-01T00:00:00Z2024 May2026-04-24T03:12:15.516Z2026-04-24T03:09:52.553ZS-EPMC110770653855411510.1093/nar/gkae216