Regulation of the specificity of the 26S proteasome endoribonuclease activity in K562 cells under the action of differentiation and apoptosis inducers

The specificity of the 26S proteasome endoribonuclease activity in proerythroleukemic K562 cells has been shown to change under the effects of inducers of erythroid differentiation inducers led to specific stimulation of RNase activity for certain mRNAs and to reduction of proteasome RNase activity for other mRNAs. The studied enzymatic activity was shown to be specifically and selectively dependent on phosphorylation of the 26S proteasome subunits, as well as on Mg and Ca ions. It was shown that the specificity of the proteasome RNase activity is regulated during differentiation and apoptosis. Selective regulation of the proteasome via the activities of different nuclease centers was suggested. This regulation may be accomplished through changes in the phosphorylation state of the proteasome subunits as well as by cation homeostasis.