1. The N‐terminus and SH2 domain of SOCS‐1 contribute to inhibition of JAK1 and JAK2 kinase activity.
The N‐terminus and SH2 domain of SOCS‐1 contribute to inhibition of JAK1 and JAK2 kinase activity. COS or 293T cells were transiently transfected with vector alone (−) or cDNAs expressing either Flag‐tagged SOCS‐1 (S1) or the SOCS‐1 deletion mutants S1Δ170–212, S1Δ1‐76&170–212, S1Δ1‐76 and S1Δ82‐212 in the presence of cDNA expressing either Flag‐tagged JAK1 (+) or JAK2 (+). (A) JAK1 kinase activity. After 48 h, cells were lysed and JAK1 proteins immunoprecipitated using anti‐JAK1 antibody. Immunoprecipitates were then subjected to an in vitro kinase assay. (B) Immunoprecipitates from (A) were split prior to kinase assay and analyzed by Western blot with anti‐Flag antibody (JAK1 proteins). (C) Protein expression levels. Lysates from (A) were analyzed by Western blot with anti‐Flag antibody (SOCS‐1 proteins). (D) JAK2 kinase activity. (E) Immunoprecipitates from (D) were split prior to kinase assay and analyzed by Western blot with anti‐Flag antibody (JAK2 proteins). (F) Protein expression levels. Lysates from (D) were analyzed by immunoprecipitation and Western blot with anti‐Flag antibody (SOCS‐1 proteins; left panel) and Western blot with either anti‐Flag (SOCS‐1 proteins; center panel) or anti‐myc antibody (Stat1 and Stat5; right panel).
Sandra E. Nicholson et al. EMBO J. 1999;18:
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