FIG. 7.

Induction of TCF and LEF target genes and signaling by AML fusion proteins. (a) Western blot analysis of the TCF and LEF target genes cyclin D1 and c-Myc protein in fusion protein-expressing U937 cells, in AML1-ETO-positive Kasumi-1 cells, and in PML-RARα-positive NB4 cells. All cells expressing one of the fusion proteins expressed high levels of plakoglobin. (b) The TCF- and LEF-dependent Topflash/Fopflash promoter system was used to analyze the effects of the fusion proteins on plakoglobin downstream signaling. The vector control, AML1, or AML1-ETO expression vector was transfected along with the reporter constructs and a Renilla luciferase reporter used for normalization purposes. AML1-ETO but not AML1 induced TCF and LEF transcriptional activity. The mean ± standard error of three independent experiments is shown. (c) The effects of AML1-ETO and PML-RARα on the c-myc promoter were analyzed in primary hematopoietic CD34⁺ progenitor cells. AML1-ETO and PML-RARα induced the TCF binding element containing the del-2 promoter. No effect of the fusion proteins on the activity of the TCF binding element-lacking del-4 construct was observed. The results of four independent experiments (mean and standard error) are shown.