Detection of ubiquitinated Stat5A in the nucleus. 32D (EpoR wt) cells were starved overnight, followed by stimulation with IL-3 in the presence or absence of MG132. Cytoplasmic and nuclear extracts were prepared from these cells. Subsequently, active Stat5 was pulled down from the extracts using the biotin-labeled double-stranded Stat5-binding oligodeoxynucleotides and subjected to Western blot analyses with antiubiquitin (α-Ub) or anti-Stat5A (α-Stat5A) antibodies.