title: The N Terminus of the Vaccinia Virus Protein F1L Is an Intrinsically Unstructured Region That Is Not Involved in Apoptosis Regulation.
abstract: Subversion of host cell apoptotic responses is a prominent feature of viral immune evasion strategies to prevent premature clearance of infected cells. Numerous poxviruses encode structural and functional homologs of the Bcl-2 family of proteins, and vaccinia virus harbors antiapoptotic F1L that potently inhibits the mitochondrial apoptotic checkpoint. Recently F1L has been assigned a caspase-9 inhibitory function attributed to an N-terminal α helical region of F1L spanning residues 1-15 (1) preceding the domain-swapped Bcl-2-like domains. Using a reconstituted caspase inhibition assay in yeast we found that unlike AcP35, a well characterized caspase-9 inhibitor from the insect virus Autographa californica multiple nucleopolyhedrovirus, F1L does not prevent caspase-9-mediated yeast cell death. Furthermore, we found that deletion of the F1L N-terminal region does not impede F1L antiapoptotic activity in the context of a viral infection. Solution analysis of the F1L N-terminal regions using small angle x-ray scattering indicates that the region of F1L spanning residues 1-50 located N-terminally from the Bcl-2 fold is an intrinsically unstructured region. We conclude that the N terminus of F1L is not involved in apoptosis inhibition and may act as a regulatory element in other signaling pathways in a manner reminiscent of other unstructured regulatory elements commonly found in mammalian prosurvival Bcl-2 members including Bcl-xL and Mcl-1.
authors.affiliation: From the La Trobe Institute for Molecular Science, Department of Biochemistry and Genetics, La Trobe University, Victoria 3086, Australia and.
authors.forename: Sofia
authors.initials: S
authors.lastname: Caria
authors.affiliation: From the La Trobe Institute for Molecular Science, Department of Biochemistry and Genetics, La Trobe University, Victoria 3086, Australia and.
authors.forename: Bevan
authors.initials: B
authors.lastname: Marshall
authors.affiliation: Li Ka Shing Institute for Virology, Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Robyn-Lee
authors.initials: RL
authors.lastname: Burton
authors.affiliation: Li Ka Shing Institute for Virology, Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Campbell
authors.affiliation: From the La Trobe Institute for Molecular Science, Department of Biochemistry and Genetics, La Trobe University, Victoria 3086, Australia and.
authors.forename: Delara
authors.initials: D
authors.lastname: Pantaki-Eimany
authors.affiliation: From the La Trobe Institute for Molecular Science, Department of Biochemistry and Genetics, La Trobe University, Victoria 3086, Australia and.
authors.forename: Christine J
authors.initials: CJ
authors.lastname: Hawkins
authors.affiliation: Li Ka Shing Institute for Virology, Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta T6G 2S2, Canada micheleb@ualberta.ca.
authors.forename: Michele
authors.initials: M
authors.lastname: Barry
authors.affiliation: From the La Trobe Institute for Molecular Science, Department of Biochemistry and Genetics, La Trobe University, Victoria 3086, Australia and m.kvansakul@latrobe.edu.au.
authors.forename: Marc
authors.identifier: 0000-0003-2639-2498
authors.initials: M
authors.lastname: Kvansakul
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism; D053838:Scattering, Small Angle; D016415:Sequence Alignment; D014615:Vaccinia / Q000378:metabolism / Q000821:virology*; D014616:Vaccinia virus / Q000737:chemistry* / Q000502:physiology; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: C507356:F1L protein, vaccinia virus; D019253:Proto-Oncogene Proteins c-bcl-2; D014764:Viral Proteins
keywords: B-cell lymphoma 2 (Bcl-2) family; apoptosis; caspases; poxvirus; protein structure; small angle x-ray scattering (SAXS); vaccinia virus