Bacteriophages must hijack the gene expression machinery of their bacterial host to efficiently replicate. Recently, we have shown that the early-expressed protein gp014 of Pseudomonas nucleus-forming phage phiKZ forms a stable complex with the host ribosomes and modulates the overall protein expression profile during phage infection. Here, we discover a nucleus-forming phage, designated Churi, that is closely related to phiKZ. Churi encodes gp335, a homolog of gp014-phiKZ, which is expressed during the early stages of infection, and its overexpression in bacterial cells interferes with bacterial growth, suggesting its role in phage-host interplay. We predict experimentally that gp335 also interacts with host r... More
Bacteriophages must hijack the gene expression machinery of their bacterial host to efficiently replicate. Recently, we have shown that the early-expressed protein gp014 of Pseudomonas nucleus-forming phage phiKZ forms a stable complex with the host ribosomes and modulates the overall protein expression profile during phage infection. Here, we discover a nucleus-forming phage, designated Churi, that is closely related to phiKZ. Churi encodes gp335, a homolog of gp014-phiKZ, which is expressed during the early stages of infection, and its overexpression in bacterial cells interferes with bacterial growth, suggesting its role in phage-host interplay. We predict experimentally that gp335 also interacts with host ribosomal proteins, similar to its homolog gp014-phiKZ, thereby strengthening its involvement in protein translation during phage infection. We further show that GFP-tagged gp335 specifically localizes by clustering around the phage nucleus and remains associated with it throughout the infection cycle. The CRISPR-Cas13-mediated deletion of gp335 reveals that the mutant phage fails to replicate efficiently, resulting in an extended latent period. Altogether, our study demonstrates that gp335 is an early-expressed protein of the Chimallivirus Churi that localizes in proximity to the phage nucleus, likely serving a role in localized translation to ensure efficient phage propagation.Author summaryBacteriophages are prokaryotic viruses that infect bacteria. Due to their relatively small genome size, they typically rely on their host s machinery for reproduction. Recently, we discovered nucleus-forming jumbophages that harbor large genomes, displaying intricate organization via nucleus-based replication. Despite their unique subcellular organization through the formation of a nucleus-like structure, similar to other phages, their protein translation machinery remains dependent on the bacterial host. In this study, we identified a novel nucleus-forming jumbophage, Churi, and demonstrated that it produces an early-expressed protein, gp335, which likely interacts with the host ribosomes. Additionally, gp335 localizes specifically near the nuclear shell, where ribosomes are presumably situated, throughout the infection cycle, likely playing a role in the translation of phage proteins on the nuclear surface. In the absence of gp335, the phage exhibits reduced reproductive efficiency, leading to slower infection and delayed cell lysis. This phage-host interplay is conserved in other nucleus-forming phages and might have evolutionary implications.
