Transcriptional activity of GATA-1 is enhanced by PML4. (A-B) PML4 enhanced GATA-1 transactivity in a luciferase reporter assay. 293T cells were cotransfected with (A) pro-AHSP-pGL3-basic (AHSP-pro) or (B) pro-PRG2- pGL3-basic (PRG2-pro) and pRL-TK in the presence or absence of GATA-1 and increased gradient of PML4 expression vectors. Transfected cells were cultured for 24 hours and lysed for measurement of luciferase activities. p300 was used as the positive control in the reporter assays. (C) PML1 did not increase GATA-1 transactivity as PML4 did. 293T cells were transfected with AHSP-pro, pRL-TK, PML1, or PML4 with or without GATA-1 as indicated. (D) Influence of truncated PML4 fragments on transactivation ability of GATA-1. The Δ400 PML mutant that cannot interact with GATA-1 also shows loss of cooperation with GATA-1. All data are representative of 3 independent experiments. Error bars represent standard error of the mean.