STUB1 overexpression promoted ubiquitination and degradation of RUNX1.
A, 293T cells were transfected with Myc–RUNX1, HA–ubiquitin, and FLAG–STUB1. Whole-cell extracts were immunoprecipitated with anti-Myc antibody, and ubiquitinated RUNX1 was detected with anti-HA antibody. RUNX1-bound STUB1 was detected with anti-FLAG. B, 293T cells were transfected with FLAG–RUNX1, HA–ubiquitin, Myc–STUB1, or Myc–STUB1-K30A. Whole-cell extracts were immunoprecipitated with anti-FLAG antibody, and ubiquitinated RUNX1 was detected with anti-HA antibody. RUNX1-bound STUB1 was detected with anti-Myc. STUB1-K30A showed reduced activity to induce RUNX1 ubiquitination. C, 293T cells were transfected with Myc–RUNX1, HA–ubiquitin, and FLAG–STUB1. Nuclear and cytoplasmic fractions were isolated and were immunoprecipitated with anti-Myc antibody, following the detection of ubiquitinated RUNX1 with anti-HA antibody. STUB1 induced RUNX1 ubiquitination mainly in the nucleus. IB, immunoblot.