Activation of a p44 pseudogene in Anaplasma phagocytophila by bacterial RNA splicing: a novel mechanism for post‐transcriptional regulation of a multigene family encoding immunodominant major outer membrane proteins

@article{Zhi2002ActivationOA,
  title={Activation of a p44 pseudogene in Anaplasma phagocytophila by bacterial RNA splicing: a novel mechanism for post‐transcriptional regulation of a multigene family encoding immunodominant major outer membrane proteins},
  author={Ning Zhi and Norio Ohashi and Yasuko Rikihisa},
  journal={Molecular Microbiology},
  year={2002},
  volume={46}
}
Immunodominant 44 kDa major outer membrane proteins of Anaplasma phagocytophila (human granulocytic ehrlichiosis agent) are encoded by the p44 multigene family. One of the paralogues, p44–18 is predominantly expressed by A. phagocytophila in mammalian hosts, but is downregulated in the arthropod vector. The expression of p44–18 was upregulated in A. phagocytophila cultivated in HL‐60 cells at 37°C compared with 24°C. However, the molecular mechanism of such gene expression was unclear, as p44… 

Anaplasma phagocytophilum MSP2(P44)-18 Predominates and Is Modified into Multiple Isoforms in Human Myeloid Cells

Proteomic and molecular approaches were used to determine that MSP2(P44)-18 is the predominant if not the only paralog expressed and is modified into multiple 42- to 44-kDa isoforms by A. phagocytophilum strain HGE1 during infection of HL-60 cells.

Analysis of Involvement of the RecF Pathway in p44 Recombination in Anaplasma phagocytophilum and in Escherichia coli by Using a Plasmid Carrying the p44 Expression and p44 Donor Loci

The results support the view that the p44 gene conversion in A. phagocytophilum occurs through the RecF pathway.

Expression of Multiple Outer Membrane Protein Sequence Variants from a Single Genomic Locus of Anaplasma phagocytophilum

Data suggest that, similarly to A. marginale, A. phagocytophilum uses combinatorial mechanisms to generate a large array of outer membrane protein variants, which has profound implications for the design of vaccines, diagnostic tests, and therapy.

Anaplasma phagocytophilum p44 mRNA Expression Is Differentially Regulated in Mammalian and Tick Host Cells: Involvement of the DNA Binding Protein ApxR

Results indicate that p44 genes and apxR are specifically up-regulated in the mammalian host environment and suggest that ApxR not only is positively autoregulated but also acts as a transcriptional regulator of p44E.

Establishment of Cloned Anaplasma phagocytophilum and Analysis of p44 Gene Conversion within an Infected Horse and Infected SCID Mice

P44E recombination was unambiguously demonstrated and similar levels of p44E convertants were detected in either the presence or absence of an acquired immune system, suggesting that T- and B-cell immune pressure was not essential for recombination and/or selection of the p 44E variants.

Mechanisms of Variable p44 Expression by Anaplasma phagocytophilum

Variations in p44 sequences at the level of the p44 expression locus occur through unidirectional conversion of the entire p44 hypervariable region including flanking regions with a corresponding sequence copied from one of the conserved donor p44 genomic loci, suggesting that the P44 antigenic repertoire within the hyper variable region is restricted.

Polymorphism and Transcription at the p44-1/p44-18 Genomic Locus in Anaplasma phagocytophilum Strains from Diverse Geographic Regions

These p44 loci provide insight into the molecular evolution and functional divergence of p44 paralogs and may serve as markers for typing strains from different geographic regions.

Rapid Sequential Changeover of Expressed p44 Genes during the Acute Phase of Anaplasma phagocytophilum Infection in Horses

Results suggest that the rapid and synchronized switch of expression is an intrinsic property of p44s reinitiated after transmission to naïve mammalian hosts and shaped upon exposure to immune plasma.

Groupings of highly similar major surface protein (p44)-encoding paralogues: a potential index of genetic diversity amongst isolates of Anaplasma phagocytophilum.

The hypothesis that sequences of paralogues in similarity groups may provide an index of adaptation of different 'strains' of A. phagocytophilum to specific reservoir hosts in different geographical locations, and any associations with infectivity for different species including humans, is raised.

Introns in the Cytolethal Distending Toxin Gene of Actinobacillus actinomycetemcomitans

The presence of introns within the cdt gene of A. actinomycetemcomitans is reported, and site-directed and deletion mutation studies of the splice site sequence indicated that sequence conservation was important in order for accurate splicing to occur.

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