title: Siva-1 promotes K-48 polyubiquitination of TRAF2 and inhibits TCR-mediated activation of NF-kappaB.
abstract: The proapoptotic protein Siva-1 plays an important role in some of the extrinsic and intrinsic apoptosis signaling pathways in cancer cells. Previously, we showed that Siva-1 inhibited the activity of the prosurvival transcription factor NF-kappaB. In the present study, upon TCR cross-linking of Jurkat T leukemia cells, we demonstrated that the inhibitory target of Siva-1 is upstream of the IKK complex in the NF-kappaB signaling pathway. Additionally, Siva-1 also suppressed the activity of another crucial transcription factor AP-1, and a common mediator of both these pathways is the adaptor protein TRAF2. Further, we observed that Siva-1 indeed interacted with TRAF2 and negatively regulated its activity by promoting K48-hnked polyubiquitination. Siva-1 specifically interacted with the ring finger domain of TRAF2, which is essential for its E3 hgase activity and its ability to subsequently activate NF-kappaB. TCR cross-linking of Jurkat T cells that lacked Siva-1 revealed significantly lowered K48- but elevated K63-ubiquitinated TRAF2 levels upon TCR cross-linking, suggesting that the differential pattern of ubiquitination in these cells essentially contributed to a robust and sustained activation of NF-kappaB. The above results demonstrated an important role for endogenous Siva-1 in negatively regulating NF-kappaB activation by targeting TRAF2.
authors.affiliation: Department of Microbiology and Immunology, University of Illinois, Chicago, IL 60612, USA.
authors.forename: Radhika
authors.initials: R
authors.lastname: Gudi
authors.forename: John
authors.initials: J
authors.lastname: Barkinge
authors.forename: Sarah
authors.initials: S
authors.lastname: Hawkins
authors.forename: Bellur
authors.initials: B
authors.lastname: Prabhakar
authors.forename: Prasad
authors.initials: P
authors.lastname: Kanteti
mesh_terms: D051017:Apoptosis Regulatory Proteins; D002460:Cell Line; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D019169:Jurkat Cells; D008239:Lysine / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D025941:Protein Interaction Mapping; D054829:RING Finger Domains; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D047992:TNF Receptor-Associated Factor 2 / Q000737:chemistry / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D051017:Apoptosis Regulatory Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D011948:Receptors, Antigen, T-Cell; C106549:SIVA1 protein, human; D047992:TNF Receptor-Associated Factor 2; D048029:TNF Receptor-Associated Factor 6; D018808:Transcription Factor AP-1; D051550:I-kappa B Kinase; D008239:Lysine