title: Uncovering the Mechanism of Forkhead-Associated Domain-Mediated TIFA Oligomerization That Plays a Central Role in Immune Responses.
abstract: Forkhead-associated (FHA) domain is the only signaling domain that recognizes phosphothreonine (pThr) specifically. TRAF-interacting protein with an FHA domain (TIFA) was shown to be involved in immune responses by binding with TRAF2 and TRAF6. We recently reported that TIFA is a dimer in solution and that, upon stimulation by TNF-α, TIFA is phosphorylated at Thr9, which triggers TIFA oligomerization via pThr9-FHA domain binding and activates nuclear factor κB (NF-κB). However, the structural mechanism for the functionally important TIFA oligomerization remains to be established. While FHA domain-pThr binding is known to mediate protein dimerization, its role in oligomerization has not been demonstrated at the structural level. Here we report the crystal structures of TIFA (residues 1-150, with the unstructured C-terminal tail truncated) and its complex with the N-terminal pThr9 peptide (residues 1-15), which show unique features in the FHA structure (intrinsic dimer and extra β-strand) and in its interaction with the pThr peptide (with residues preceding rather than following pThr). These structural features support previous and additional functional analyses. Furthermore, the structure of the complex suggests that the pThr9-FHA domain interaction can occur only between different sets of dimers rather than between the two protomers within a dimer, providing the structural mechanism for TIFA oligomerization. Our results uncover the mechanism of FHA domain-mediated oligomerization in a key step of immune responses and expand the paradigm of FHA domain structure and function.
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.|Taiwan International Graduate Program, Academia Sinica , Taipei, Taiwan.|Institute of Biochemical Sciences, Department of Chemistry, National Tsing Hua University , Hsinchu, Taiwan.
authors.forename: Jui-Hung
authors.initials: JH
authors.lastname: Weng
authors.affiliation: Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center , Hsinchu, Taiwan.
authors.forename: Yin-Cheng
authors.initials: YC
authors.lastname: Hsieh
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.|Taiwan International Graduate Program, Academia Sinica , Taipei, Taiwan.|Institute of Biochemical Sciences, National Taiwan University , Taipei, Taiwan.
authors.forename: Chia-Chi Flora
authors.initials: CC
authors.lastname: Huang
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.|Institute of Biochemical Sciences, National Taiwan University , Taipei, Taiwan.
authors.forename: Tong-You Wade
authors.initials: TY
authors.lastname: Wei
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.|Institute of Biochemical Sciences, National Taiwan University , Taipei, Taiwan.
authors.forename: Liang-Hin
authors.initials: LH
authors.lastname: Lim
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.
authors.forename: Yu-Hou
authors.initials: YH
authors.lastname: Chen
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.
authors.forename: Meng-Ru
authors.initials: MR
authors.lastname: Ho
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.
authors.forename: Iren
authors.initials: I
authors.lastname: Wang
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.
authors.forename: Kai-Fa
authors.initials: KF
authors.lastname: Huang
authors.affiliation: Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center , Hsinchu, Taiwan.
authors.forename: Chun-Jung
authors.initials: CJ
authors.lastname: Chen
authors.affiliation: Institute of Biological Chemistry, Academia Sinica , Taipei, Taiwan.|Taiwan International Graduate Program, Academia Sinica , Taipei, Taiwan.|Institute of Biochemical Sciences, National Taiwan University , Taipei, Taiwan.
authors.forename: Ming-Daw
authors.initials: MD
authors.lastname: Tsai
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D010769:Phosphothreonine / Q000737:chemistry / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D017433:Protein Structure, Secondary
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D010455:Peptides; C446759:TIFA protein, human; D010769:Phosphothreonine