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Phage Phenomics: Physiological Approaches to Characterize Novel Viral Proteins
Published on: June 11, 2015
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An essential and highly selective protein import pathway encoded by nucleus-forming phage
Chase J Morgan1, Eray Enustun1, Emily G Armbruster1
1School of Biological Sciences, Division of Molecular Biology, University of California San Diego, La Jolla, CA 92093.
Summary
Researchers discovered a novel protein import pathway in chimalliviruses, involving a protein called PicA (Protein importer of chimalliviruses A). This pathway is crucial for phage replication and understanding viral evolution.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Protein localization is vital for cellular functions in all life forms.
- Chimalliviridae phages create a nucleus-like compartment using chimallin (ChmA), separating viral DNA replication from the cytoplasm.
- Selective protein partitioning between the phage nucleus and host cytoplasm is observed, but the underlying mechanisms are unknown.
Purpose of the Study:
- To identify the genes and signals responsible for selective protein import into the chimallivirus nucleus.
- To elucidate the mechanism of protein trafficking across the phage nuclear shell.
- To understand the role of this pathway in chimallivirus replication and evolution.
Main Methods:
- Identification of a species-specific surface-exposed region on a phage intranuclear protein.
- Characterization of a conserved protein, PicA (Protein importer of chimalliviruses A), involved in cargo protein trafficking.
- Analysis of a defective cargo protein that binds but does not enter the nucleus.
- CRISPR interference-ART (CRISPRi-ART) mediated knockdown of PicA expression.
Main Results:
- Two key components of the protein import pathway were identified: a phage protein surface region and PicA.
- A defective cargo protein provided insights into the nuclear protein trafficking mechanism.
- PicA is essential for chimallivirus replication early in the cycle.
- A multistep model for the Protein Import Chimallivirus pathway was proposed, involving surface-targeted amino acids and PicA-mediated licensing.
Conclusions:
- The Protein Import Chimallivirus pathway involves specific protein targeting and PicA-mediated entry.
- The divergence of this pathway suggests its role in phage evolution and host-phage interactions.
- PicA is a critical factor for chimallivirus nuclear import and replication.
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