Fig. 3. Characterization of PCTAIRE-1 kinase-dead mutants. A, Western blot analysis of HA-tagged PCTAIRE-1 wild-type (Lane 2) and D304N (Lane 3) and K194A (Lane 4) point mutants upon ectopic expression in HeLa cells. HeLa cells transfected with empty vector (pcDNA3-HA) were used as a control (Lane 1). B, wild-type or kinase-dead HA-tagged PCTAIRE-1 mutants were immunoprecipitated from HeLa cell extracts, and kinase activity was determined as described in "Materials and Methods."