EKLF/KLF1 is ubiquitinated in vivo and its stability is regulated by activation domain sequences through the 26S proteasome

Erythroid Krüppel-like factor (EKLF/KLF1) is an erythroid specific, C(2)H(2) zinc finger transcription factor that is essential for the proper chromatin structure and expression of the adult beta-globin gene. Herein, we determine that 26S proteasome inhibitors lead to an accumulation of EKLF protein in murine erythroleukemia (MEL) cells. In addition, EKLF half-life in both MEL cells (<3h) and fetal liver cells (between 6 and 9h) is stabilized in the presence of these inhibitors. EKLF is ubiquitinated in vivo, however its modification does not rely on a particular internal lysine. Finally, EKLF contains two PEST sequences within its N-terminus that have no effect on the ability of EKLF to be ubiquitinated but contribute to its destabilization.