Independent of it is kinase activity, the TGF-activated kinase 1 (TAK1) mediates LMP1 signaling complex formation, NEMO ubiquitination and subsequent IKK2 activation. activity assays were performed. JNK activation by LMP1 was substantially reduced in all three knockout mice64. The lymphoblastoid cell line LCL 1C3 (provided by J. Mautner) was generated by infection of primary human B cells with B95.8 EBV. BL41:NGFR-LMP1wt cells (provided by J. Mautner), EBV-negative BL41 Burkitt lymphoma cells and LCL721 have been described and were taken from own laboratory stocks65C67. The transgene (tg)-positive carcinoma cell line 53.234a and corresponding tg mice or genes of PTLD099 and PTLD880 were amplified by PCR and the signaling domains were sequenced. Primer sequences are given in Supplementary Table?1. Lymphoblastoid cell line LCL877 was derived from primary cells of the same PTLD biopsy that gave rise to PTLD880, but was infected with EBV laboratory strain B95.8. Cells obtained as described above were plated in medium with cyclosporine A containing 10?l/well of filtered (0.7?m) supernatant from EBV-producing cell line B95.8. Cells were further cultivated and expanded as described above for PTLD cell lines. LCL.NGFR-LMP1.6 cells were established by infection and conditional transformation of peripheral KDM5C antibody blood B cells of an adult EBV-negative donor with recombinant maxi-EBV 2264.19, carrying NGFR-LMP1 instead of wildtype LMP153. Initial outgrowth of infected B cells was supported by plating Pyridostatin PBMCs on top of an adherent layer of irradiated LL8 mouse fibroblasts expressing human CD40L68. At day 14, the cells Pyridostatin were removed from the feeder layer and since then continuously cultivated in the presence of crosslinking antibodies (see NGFR-LMP1 crosslinking) to maintain LMP1 signals and proliferation. After 8 weeks, the culture expanded to approximately 106 cells and was used for experiments. Ethics We complied with all relevant ethical regulations for work with human participants. Anonymised human PTLD biopsies and blood from a healthy human donor were obtained with informed consent as approved by the Institutional Review Board (Ethics Commission of the Faculty of Medicine of the Ludwig-Maximilians-University Munich, project no. 071C06C075C06). Plasmids The plasmids pCMV-HA-LMP1 wildtype, pCMV-HA-LMP1(AAA/371C386) harboring a P204xQxT to AxAxA mutation within CTAR1 and lacking the 16 C-terminal amino acids of CTAR2, pCMV-HA-LMP1(AAA/Y384G), pSV-LMP1, pSV-LMP1(Y384G), pcDNA3-Flag-IKK2, and pRK5-HA-JNK1 have been described16,49. The vector pSV-NGFR-LMP1 encoding a fusion protein of aa 1C279 of human low affinity p75 NGF-receptor and aa 196C386 of LMP1 has been described17,48. pCMV5-TPL2wt.MT (provided by C. Patriotis) and pcDNA3-Flag-p105 (provided by D. Krappmann) have been described69,70. The vector pEF4C-3xFlag-IKKwt (NEMO) was a kind gift of D. Krappmann. pRK5-HA-Ubiquitin K63 (all lysines mutated to arginines except of K63) was obtained from Addgene and has been described71. Retroviral transduction NGFR-LMP1 wildtype and NGFR-LMP1(Y384G) were subcloned from pSV-NGFR-LMP1 into the retroviral vector pSF91-IRES-GFP-WPRE (provided by C. Baum)72. For virus production, phoenix-gp cells were transfected with pSF91-NGFR-LMP1-IRES-GFP-WPRE, gag-pol vector and pEcoEnv expressing ecotropic Env protein as described21. MEFs were infected and sorted for low Pyridostatin and comparable GFP expression levels using a MoFlo cell sorter (Beckman Coulter). NGFR-LMP1 expression at the cell surface of the resulting bulk cultures was analysed by staining with Alexa647-conjugated NGFR antibody (#557714, BD Pharmingen) and subsequent flow cytometry using a FACS Calibur flow cytometer (Becton Dickinson). Data processing was performed with FlowJo software. CRISPR/Cas9 gene targeting U6gRNA-Cas9-2A-GFP gene targeting vectors were obtained from Sigma-Aldrich and expressed Cas9, GFP and the following gRNAs: murine MM0000145296 (thanks Bill Sugden and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available. Publishers note Springer Nature remains neutral with regard to Pyridostatin jurisdictional claims in Pyridostatin published maps and institutional affiliations. Supplementary information Supplementary information is available for this paper at 10.1038/s41467-020-14502-x..