(A) Immunoblot analysis of immunoprecipitated chMyD88 from chicken DF1 cells transfected with indicated plasmids. Immunoprecipitation was carried out with anti-FLAG antibody and then probed with indicated antibodies. (B) Immunoblot analysis of lysates from chicken DF1 cells transfected with indicated plasmids. (C) K118 and K124 of chMyD88 are required for the downregulation of chMyD88 by chSPOP. Truncated chMyD88 K143R constructs consisting of the death-like and intermediate domain with additional K55R, K118R, K119R, or K124R point mutations were transfected into chicken DF1 cells. Expression of the K143R constructs of chMyD88 was detected by anti-FLAG antibody. (D) Mutations at K118, K124, and K143 reduce the polyubiquitination of chMyD88. Wild-type, K118R, K124R, or K143R chMyD88 was transfected into chicken DF1 cells alongside chSPOP. chMyD88 was immunoprecipitated by anti-FLAG antibody, and by immunoblotting performed with indicated antibodies.