The manipulation of host transcription by the ANKH effector of legionella.

Legionnaires disease;legionella;AnkH;LARP7;transcription;LCV;T4SS;7SK snRNP

Juanita E. Von Dwingelo

University:University of Louisville

Department:Microbiology and Immunology

关键词: Legionnaires disease;    legionella;    AnkH;    LARP7;    transcription;    LCV;    T4SS;    7SK snRNP;   

Others  :  https://ir.library.louisville.edu/cgi/viewcontent.cgi?article=4564&context=etd

美国|英语

来源: The Universite of Louisville's Institutional Repository

【 摘 要 】

Legionella pneumophila is a Gram-negative facultative intracellular bacterium that can be found dispersed throughout freshwater environments, where it primarily parasitizes amoebae and other protozoan species. Humans are an accidental host for L. pneumophila, and infection occurs upon inhalation of aerosolized water droplets that contain the bacteria. L. pneumophila is the causative agent of Legionnaires’ Disease, which is the result of intracellular proliferation within alveolar macrophages. Pathogenesis of L. pneumophila is dependent on the Dot/Icm type 4 secretion system (T4SS) apparatus, which is comprised of 27 proteins and is responsible for translocating over 330 effector proteins into the host cell. Many of these effector proteins contain eukaryotic-like domains and motifs, which have been acquired through interkingdom horizontal gene transfer from various aquatic eukaryotic hosts. While L. pneumophila contains such a large repertoire of effector proteins, most of them are not required for survival and proliferation in mammalian macrophages, since single deletion of most effectors does not result in a defect in intracellular replication. Although this could be explained by effector redundancy, it is more likely that these effector proteins constitute a tool box utilized by L. pneumophila to survive and replicate within numerous species of protozoa. One effector identified, that when deleted results in a defect in intracellular replication, is the AnkH effector. It has been shown that AnkH is required for robust intracellular replication of L. pneumophila within amoebae, human macrophages and the A/J mouse model of infection. It has previously been shown that AnkH is an effector that contains ankyrin repeats, which are eukaryotic-like domains, and function as a scaffold for protein-protein interactions. Other than requirement of AnkH during intracellular replication, its function and host targets remain unknown and are the focus of this work. We further characterized AnkH to elucidate its host target and function during infection of macrophages. Using a yeast 2 hybrid system, seven potential host interacting partners have been identified and one interacting partner, human La related protein 7 (LARP7), has been confirmed via co-immunoprecipitation. LARP7 is a component of a transcriptional regulatory complex, 7SK snRNP complex that negatively regulates transcriptional elongation. The AnkH -LARP7 interaction blocks LARP7 binding to components of the 7SK snRNP complex, resulting in the disruption of the complex. Knockdown of LARP7 using LARP7 specific RNAi results in a significant growth defect of the WT strain during infection of macrophages, and the growth defect of the ∆ankH null mutant becomes more