Nuclear Translocated Ehrlichia chaffeensis Ankyrin Protein Interacts with a Specific Adenine-Rich Motif of Host Promoter and Intronic Alu Elements

Ehrlichiae are obligately intracellular bacteria that reside and replicate in phagocytes by circumventing host cell defenses and modulating cellular processes, including host cell gene transcription. However, the mechanisms by which ehrlichiae influence host gene transcription have largely remained undetermined. Numerous ankyrin and tandem repeat-containing proteins associated with host-pathogen interactions have been identified inEhrlichia species, but their roles in pathobiology are unknown. In this study, we determined by confocal immunofluorescence microscopy and by immunodetection in purified nuclear extracts that the ankyrin repeat-containing protein p200 is translocated to the nuclei ofEhrlichia- infected monocytes. Chromatin immunoprecipitation (ChIP) with DNA sequencing revealed anEhrlichia chaffeensis p200 interaction located within host promoter and intronicAlu-Sx elements, the most abundant repetitive elements in the human genome. A specific adenine-rich (mid-A-stretch) motif withinAlu-Sx elements was identified using electrophoretic mobility shift and NoShift assays. Whole-genome analysis with ChIP and DNA microarray analysis (ChIP-chip) determined that genes (n = 456) with promoterAlu elements primarily related to transcription, apoptosis, ATPase activity, and structural proteins associated with the nucleus and membrane-bound organelles were the primary targets of p200. Several p200 target genes (encoding tumor necrosis factor alpha, Stat1, and CD48) associated with ehrlichial pathobiology were strongly upregulated during infection, as determined by quantitative PCR. This is the first study to identify a nuclear translocation of bacterially encoded protein byE. chaffeensis and to identify a specific binding motif and genes that are primary targets of a novel molecular strategy to reprogram host cell gene expression to promote survival of the pathogen.