REPROGRAMMING OF NUCLEAR PROTEASOMES IN K562 CELLS UNDERGOING APOPTOSIS.
I. EFFECT OF GLUTATHIONE-DEPLETING AGENT, DIETHYLMALEATE
A. S. Tsimokha,1, * A. G. Mittenberg,1 V. A. Kulichkova,1
Yu. Ya. Vatajok,1 T. N. Moiseeva,1 I. N. Evteeva,1
Yu. B. Ermolaeva,1 L. N. Gause,2
I. M. Konstantinova 1
1 Institute of Cytology RAS, St. Petersburg, and 2 N. K. Koltsov Institute of Development
Biology RAS, Moscow;
* e-mail: atsimokha@mail.cytspb.rssi.ru
Here we have studied changes in the subunit composition, phosphorylation state and enzymatic activities of
26S proteasomes in cells undergoing the programmed cell death. Apoptosis in proerythroleukemic K562 cells
was induced by glutathione-depleting agent, diethylmaleate (DEM). We have shown for the first time that proteasomes
isolated from the nuclei of control and induces K562 cells differ in their subunit patterns, as well as in
the phosphorylation state of subunits on threonine and tyrosine residues. We observed trypsin- and chymotrypsin-
like activities on nuclear proteasomes and the specificity of proteasomal nucleolysis of several individual
messenger RNAs (c-fos and c-myc) to be changed under effect of DEM on K562 cells. Treatment of K562 cells
with DEM leads to modification of zeta/α5 and iota/α6 proteasomal subunits associated with RNAse activity of
proteasomes. These findings confirm our hypothesis about so-called reprogramming of nuclear proteasome population
in undergoing apoptosis K562 cells which is manifested by the changes in proteasomal composition,
phosphorylation state, and enzymatic activities during the programmed cell death.
Key words: apoptosis, diethylmaleate, nuclear proteasomes, phosphorylation, proteolytic
activity, ribonucleases, threonine, tyrosine
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