Dimerization ability of adult T‐cell leukemia (ATL)‐type Helios isoforms. In vitro dimerization assays by co‐immunoprecipitation between ATL‐type Helios and wild‐type Helios or Ikaros proteins. 293T cells were transfected with the indicated combination of expression vectors and subjected to co‐immunoprecipitation analyses (top panels). Arrowheads indicate the complex of FLAG and HA‐tagged proteins. Middle and bottom panels show the input samples. Hel‐1 (a) and Hel‐ΔC (b) included as positive and negative controls, respectively. ATL‐specific isoforms, Hel‐5 (c), Hel‐6 (d), Hel‐v1 (e), and Hel‐v2 (f) were tested. IB, immunoblot; IP, immunoprecipitant.