TCL1 suppresses PTPROt promoter in K562 cells by inhibiting c-fos transcription and c-jun activity. K562 cells were transfected with pGL3-basic or PTPt-P-Luc and TCL1 expression vector as indicated. (A) Normalized luciferase activity (firefly/Renilla) is reported as fold change over pGL3-basic activity. Error bars represent SD. P values were calculated using the Student t test. (B) TCL1 expression in transfected cells was confirmed by Western blot. The experiment was repeated twice with 5 replicates each. (C) Western blot analysis of whole cell extracts prepared from K562 cells stably expressing TCL1 using the antibodies indicated in the figure. Quantification of bands using AlphaImager (Alpha Innotech) represented as column graph. Error bars represent SD. (D) Possible mechanisms of AP-1 inhibition by TCL1. (E) JNK activity assay was performed using extracts from K562 cells transfected with vector or stably expressing TCL1. ³²P-Labeled substrate (c-jun) was resolved on 10% SDS-PAGE and subjected to autoradiography and immunoblotting with anti-GST antibody. The experiment was repeated twice with duplicates in each run. Quantification of bands represented as column graph. Error bars represent SD. P values were calculated using the Student t test. (F) Expression of pre-c-fos normalized to β-actin was analyzed by real-time RT-PCR on total RNA from vector control and TCL1-expressing K562 cells. The experiment was repeated twice with triplicate measurements. Error bars represent SD. P values were calculated using the Student t test.