Construction and expression of the Flag-tagged PML-RARA fusion protein. (A) Schematic for 2 major isoforms of PML-RARA fusion proteins. Functional domains within the PML moiety are indicated. The dashed lines indicate the break points in the fusion proteins. RING, the RING finger; B1 and B2, B-box motifs; C-C, coiled-coil. (B) Schematic representation for the Flag-tagged long (top) and short (bottom) isoforms of the PML-RARA fusion proteins with the indicated point mutations. Bold letters indicate amino acid substitutions inside the B2 domain of the PML part. (C) Immunoblotting analysis for the expression levels of the short and long isoforms of Flag-tagged PML-RARA (PR-S-WT and PR-L-WT, respectively) in HeLa cells transfected with the indicated doses of plasmids. The levels of endogenous Tubulin expression were detected as loading controls.