title: Intramolecular dimerization is required for the chlamydia-secreted protease CPAF to degrade host transcriptional factors.
abstract: We previously identified a chlamydial protein designated CPAF (chlamydia protease/proteasome-like activity factor) that is secreted into host cell cytosol for degrading host transcription factors required for major histocompatibility complex antigen expression. Here we report that CPAF, synthesized as a 70-kDa proprotein, is processed into two fragments (designated CPAFn and CPAFc) to form intramolecular dimers that are much more stable than the naïve CPAF. Precipitation with antibodies that recognized CPAF dimers removed the proteolytic activity responsible for degrading host transcription factor RFX5 from chlamydia-infected host cell cytosol, while precipitation with antibodies that recognized free CPAF fragments alone did not remove this activity. Separation of CPAFn from CPAFc resulted in a loss of proteolytic activity. Furthermore, neither expressed full-length CPAF that was not processed nor coexpressed CPAFn and CPAFc fragments that failed to form dimers degraded RFX5. These observations demonstrate that intramolecular dimerization is required for CPAF to degrade host transcription factors, a strategy that is utilized by an obligate intracellular bacterial species to evade host defenses.
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Dong
authors.forename: Jyotika
authors.initials: J
authors.lastname: Sharma
authors.forename: Yanming
authors.initials: Y
authors.lastname: Xiao
authors.forename: Youmin
authors.initials: Y
authors.lastname: Zhong
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhong
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D002689:Chlamydia / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism; D002690:Chlamydia Infections / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism; D003001:Cloning, Molecular; D019281:Dimerization; D010450:Endopeptidases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006367:HeLa Cells; D006790:Host-Parasite Interactions; D006801:Humans; D011233:Precipitin Tests; D014157:Transcription Factors / Q000378:metabolism*; D019076:Transgenes
chemical_list: D000911:Antibodies, Monoclonal; D014157:Transcription Factors; D010450:Endopeptidases