Stable overexpression of specific segments of the P2P-R protein in human MCF-7 cells promotes camptothecin-induced apoptosis.
The stable overexpression of near full-length P2P-R protein in human Saos 2 cells restricts cell cycle progression by inducing mitotic arrest at prometaphase and mitotic apoptosis (Gao and Scott, 2002). Those effects of P2P-R were observed in Saos-2 cells that lack p53 and employ a caspase-3-dependent apoptotic signaling pathway. The current studies were performed to evaluate if overexpression of specific segments of the P2P-R protein promote apoptosis in human MCF-7 cells that contain p53 and employ a different apoptotic signaling pathway. Since segments of P2P-R were found not to induce apoptosis independently, the ability of three different P2P-R segments to promote camptothecin-induced apoptosis was evaluated following their stable transfection and expression in MCF-7 cells. Relative to full-length P2P-R (1-1560 aa), the three P2P-R segments used in these studies included: P2P-R-2 (761-1560 aa), P2P-R-3 (1156-1560 aa), and P2P-R-4 (1314-1560 aa). The results document that overexpression of P2P-R-2 and P2P-R-3 promotes camptothecin-induced apoptosis by three to fivefold when assayed by flow cytometric analysis of apoptotic sub 2n cell populations or by TUNEL assays. In contrast, P2P-R-4 had no effect on apoptosis. These results suggest that the ability of P2P-R to promote camptothecin-induced apoptosis in MCF-7 cells involves a specific region (1156-1314 aa) that exists within P2P-R. The data presented also show that the p53 binding domain of P2P-R overlaps with the apoptosis-associated region and previous studies documented that this region of P2P-R also binds single-strand nucleotides (Witte and Scott, 1997). Therefore, P2P-R-promoted apoptosis induced by camptothecin may be influenced by such interactions.
Gao
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Department of Pathology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
Scott
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D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D002166:Camptothecin / Q000494:pharmacology*; D002352:Carrier Proteins; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000502:physiology; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D000972:Antineoplastic Agents, Phytogenic; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; C104647:PRKRA protein, human; D010446:Peptide Fragments; D016601:RNA-Binding Proteins; C491290:Rbbp6 protein, mouse; D016159:Tumor Suppressor Protein p53; D002166:Camptothecin