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

  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},
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.



Transcriptional Analysis of p30 Major Outer Membrane Multigene Family of Ehrlichiacanis in Dogs, Ticks, and Cell Culture at Different Temperatures

Analysis of differential expression ofp30 multigenes in dogs, ticks, or monocyte cell cultures would help in understanding the role of these gene products in pathogenesis and E. canis transmission as well as in designing a rational vaccine candidate immunogenic against canine ehrlichiosis.

Analysis of Transcriptionally Active Gene Clusters of Major Outer Membrane Protein Multigene Family in Ehrlichia canis and E. chaffeensis

The results suggest that the gene organization of the clusters and the gene locus are conserved between two species of Ehrlichia to maintain a unique transcriptional mechanism for adaptation to environmental changes common to them.

Transcript Heterogeneity of the p44 Multigene Family in a Human Granulocytic Ehrlichiosis Agent Transmitted by Ticks

Phylogenetic analysis of the 20 different p44 transcripts revealed that the major transcripts found in mammals and ticks were distinct, suggesting a difference in surface properties between populations of the HGE agent in different host environments.

Multiple p44 Genes Encoding Major Outer Membrane Proteins Are Expressed in the Human Granulocytic Ehrlichiosis Agent*

Findings showed that p44 multigenes have several active expression sites and the expression is regulated at transcriptional level, suggesting a potentially unique mechanism for generating the diversity in major antigenic outer membrane proteins of the HGE agent.

Immunodominant Major Outer Membrane Proteins ofEhrlichia chaffeensis Are Encoded by a Polymorphic Multigene Family

Findings suggest that the 30-kDa-range proteins of E. chaffeensis represent a family of antigenically related homologous proteins encoded by a single gene family.

Cloning and Characterization of Multigenes Encoding the Immunodominant 30-Kilodalton Major Outer Membrane Proteins ofEhrlichia canis and Application of the Recombinant Protein for Serodiagnosis

The findings suggest that the rP30 antigen provides a simple, consistent, and rapid serodiagnosis for canine ehrlichiosis, and will greatly facilitate understanding pathogenesis and immunologic study of canine E. canis.

Cloning and Expression of the 44-Kilodalton Major Outer Membrane Protein Gene of the Human Granulocytic Ehrlichiosis Agent and Application of the Recombinant Protein to Serodiagnosis

The use of the affinity-purified rP44 protein as antigen would provide a more specific, consistent, and simpler serodiagnosis for HGE than the use of whole infected cells or purified HGE agents.

Characterization and Transcriptional Analysis of Gene Clusters for a Type IV Secretion Machinery in Human Granulocytic and Monocytic Ehrlichiosis Agents

This unique regulation of gene expression for the type IV secretion system may be associated with intracellular survival and replication of Anaplasma and Ehrlichia spp.

Antigenic Variation of Anaplasma marginale by Expression of MSP2 Mosaics

It is shown here that the major outer membrane protein of A. marginale, MSP2, is encoded on a polycistronic mRNA that is polymorphic and encodes numerous amino acid sequence variants in bloodstream populations of the tick-borne pathogen.

The genome sequence of Rickettsia prowazekii and the origin of mitochondria

The complete genome sequence of the obligate intracellular parasite Rickettsia prowazekii, the causative agent of epidemic typhus, is described, which contains 834 protein-coding genes and is more closely related to mitochondria than is any other microbe studied so far.