REGULATION OF THE 26S PROTEASOMES' ENDORIBONUCLEASE ACTIVITY SPECIFICITY IN K562 CELLS UNDER EFFECT OF
DIFFERENTIATION AND APOPTOSIS INDUCTORS
A. G. Mittenberg,1,* T. N. Moiseeva,1 I. V. Pugacheva,1
V. A. Kulichkova,1 A. S. Tsimokha,1 L. N. Gause,2
I. M. Konstantinova 1
1 Institute of Cytology RAS, St. Petersburg, and
2 N. K. Koltsov Institute of Developmental Biology RAS, Moscow;
* e-mail: agm@mail.cytspb.rssi.ru
The specificity of 26S proteasomes' endoribonuclease activity has been shown to be changed under effect of
erythroid differentiation (hemin) and programmed cell death (diethylmaleate) inductors in proerythroleukemic K562
cells. Treatment of K562 cells with apoptosis and differentiation inductors leads to the specific stimulation of
RNase activity towards certain mRNA and to reduction of proteasome RNase activity towards other mRNA. The enzymatic
activity under study has been demonstrated to be specifically and selectively dependent on phosphorylation of 26S
proteasome subunits as well as on Mg and Ca ions. The conclusion is drawn that the specificity of the proteasomes'
RNAse activity is regulated during differentiation and apoptosis, and selective regulation of the activity of
different nuclease centers is suggested, the mechanism involving changes in phosphorylation of proteasome subunits
and cation homeostasis.
Key words: proteasomes, ribonucleases, mRNA stability, phosphorylation, differentiation,
apoptosis, diethylmaleate, hemin
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