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The role of host protein YajQ in the temporal control of transcription in bacteriophage Phi6.

ABSTRACT: Bacteriophage Phi6 contains three dsRNA genomic segments L, M, and S. The RNA is located inside a core particle composed of multiple copies of a major structural protein, an RNA-dependent RNA polymerase, a hexameric NTPase, and an auxiliary protein. The virion RNA polymerase in the core particle transcribes segments M and S in vitro. Yet early in infection, the transcription of L is highly active. Late in infection, transcription of L is low, and that of M and S is high. A host protein encoded by yajQ is responsible for the activation of L transcription. Knockout mutants of yajQ do not support the replication of Phi6, although they do support the replication of distantly related members of the Cystoviridae. Phi6 can mutate to independence of YajQ. This requires two mutations in the gene for the RNA-dependent RNA polymerase. YajQ acts indirectly on the polymerase by binding to P1, the major structural protein of the core. Previous studies have shown that the activity of the polymerase in the core is controlled by the conformation of the core particle structure.

SUBMITTER: Qiao X

PROVIDER: S-EPMC2572959 | biostudies-literature | 2008 Oct

REPOSITORIES: biostudies-literature

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The role of host protein YajQ in the temporal control of transcription in bacteriophage Phi6.

Qiao Xueying X Sun Yang Y Qiao Jian J Mindich Leonard L

Proceedings of the National Academy of Sciences of the United States of America 20081003 41

Bacteriophage Phi6 contains three dsRNA genomic segments L, M, and S. The RNA is located inside a core particle composed of multiple copies of a major structural protein, an RNA-dependent RNA polymerase, a hexameric NTPase, and an auxiliary protein. The virion RNA polymerase in the core particle transcribes segments M and S in vitro. Yet early in infection, the transcription of L is highly active. Late in infection, transcription of L is low, and that of M and S is high. A host protein encoded b ...[more]

PMID: 18836083

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Project description:BackgroundCystoviruses have a phospholipid envelope around their nucleocapsid. Such a feature is unique among bacterial viruses (i.e., bacteriophages) and the mechanisms of virion envelopment within a bacterial host are largely unknown. The cystovirus Pseudomonas phage phi6 has an envelope that harbors five viral membrane proteins and phospholipids derived from the cytoplasmic membrane of its Gram-negative host. The phi6 major envelope protein P9 and the non-structural protein P12 are essential for the envelopment of its virions. Co-expression of P9 and P12 in a Pseudomonas host results in the formation of intracellular vesicles that are potential intermediates in the phi6 virion assembly pathway. This study evaluated the minimum requirements for the formation of phi6-specific vesicles and the possibility to localize P9-tagged heterologous proteins into such structures in Escherichia coli.ResultsUsing transmission electron microscopy, we detected membranous structures in the cytoplasm of E. coli cells expressing P9. The density of the P9-specific membrane fraction was lower (approximately 1.13 g/cm3 in sucrose) than the densities of the bacterial cytoplasmic and outer membrane fractions. A P9-GFP fusion protein was used to study the targeting of heterologous proteins into P9 vesicles. Production of the GFP-tagged P9 vesicles required P12, which protected the fusion protein against proteolytic cleavage. Isolated vesicles contained predominantly P9-GFP, suggesting selective incorporation of P9-tagged fusion proteins into the vesicles.ConclusionsOur results demonstrate that the phi6 major envelope protein P9 can trigger formation of cytoplasmic membrane structures in E. coli in the absence of any other viral protein. Intracellular membrane structures are rare in bacteria, thus making them ideal chasses for cell-based vesicle production. The possibility to locate heterologous proteins into the P9-lipid vesicles facilitates the production of vesicular structures with novel properties. Such products have potential use in biotechnology and biomedicine.

Dataset Information

The role of host protein YajQ in the temporal control of transcription in bacteriophage Phi6.

Publications

The role of host protein YajQ in the temporal control of transcription in bacteriophage Phi6.

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