LOCALIZATION OF PROTEASOMAL ANTIGENS DURING DIFFERENT PHASES OF THE CELL-CYCLE IN HELA-CELLS

We localized two different proteasome-associated epitopes with the use of two specific monoclonal antibodies, MCP21 and anti-p25, in interph ase and mitotic HeLa cells cultured in vitro. We provide evidence for an association of those antigens with the spindle poles in metaphase a nd with the midbody region in anaphase and telophase. Triton-nonextrac table structures are also labeled in interphase. More over, the labeli ng pattern of interphase cells obtained with the mono clonal antibodie s MCP21 and anti-p25 differs considerably, and in the case of MCP21 di splays clear cell cycle-specific changes: nuclear labeling is absent o r very weak in G(1) and S phases of the cell cycle, whereas it is stro ng in G(2) phase. This might reflect the existence of different subpop ulations of proteasomes in the cell.