title: Multiple Orientia tsutsugamushi ankyrin repeat proteins interact with SCF1 ubiquitin ligase complex and eukaryotic elongation factor 1 α.
abstract: BACKGROUND
  Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium. Previously, a large number of genes that encode proteins containing eukaryotic protein-protein interaction motifs such as ankyrin-repeat (Ank) domains were identified in the O. tsutsugamushi genome. However, little is known about the Ank protein function in O. tsutsugamushi.
  
  
  RESULTS
  To characterize the function of Ank proteins, we investigated a group of Ank proteins containing an F-box-like domain in the C-terminus in addition to the Ank domains. All nine selected ank genes were expressed at the transcriptional level in host cells infected with O. tsutsugamushi, and specific antibody responses against three Ank proteins were detected in the serum from human patients, indicating an active expression of the bacterial Ank proteins post infection. When ectopically expressed in HeLa cells, the Ank proteins of O. tsutsugamushi were consistently found in the nucleus and/or cytoplasm. In GST pull-down assays, multiple Ank proteins specifically interacted with Cullin1 and Skp1, core components of the SCF1 ubiquitin ligase complex, as well as the eukaryotic elongation factor 1 α (EF1α). Moreover, one Ank protein co-localized with the identified host targets and induced downregulation of EF1α potentially via enhanced ubiquitination. The downregulation of EF1α was observed consistently in diverse host cell types infected with O. tsutsugamushi.
  
  
  CONCLUSIONS
  These results suggest that conserved targeting and subsequent degradation of EF1α by multiple O. tsutsugamushi Ank proteins could be a novel bacterial strategy for replication and/or pathogenesis during mammalian host infection.
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Chan-Ki
authors.initials: CK
authors.lastname: Min
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Ye-Jin
authors.initials: YJ
authors.lastname: Kwon
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Na-Young
authors.initials: NY
authors.lastname: Ha
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Bon-A
authors.initials: BA
authors.lastname: Cho
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Jo-Min
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Eun-Kyung
authors.initials: EK
authors.lastname: Kwon
authors.affiliation: Divisions of Infectious Diseases, Chungnam National University Hospital, Daejeon, Republic of Korea.
authors.forename: Yeon-Sook
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Myung-Sik
authors.initials: MS
authors.lastname: Choi
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Ik-Sang
authors.initials: IS
authors.lastname: Kim
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine, Seoul, Republic of Korea; Institute of Endemic Disease, Seoul National University Medical Research Center and Bundang Hospital, Seoul, Republic of Korea.
authors.forename: Nam-Hyuk
authors.initials: NH
authors.lastname: Cho
mesh_terms: D017089:Ankyrin Repeat / Q000502:physiology*; D017487:Ankyrins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015977:Eukaryotic Initiation Factor-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D012285:Orientia tsutsugamushi / Q000235:genetics / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism*
chemical_list: D017487:Ankyrins; D001426:Bacterial Proteins; D015977:Eukaryotic Initiation Factor-1; D043743:Ubiquitin-Protein Ligase Complexes