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Miao S.,PLA Fourth Military Medical University | Zhang H.,Laboratory Animal Research Center | Wang S.,PLA Fourth Military Medical University | Sun J.,PLA Fourth Military Medical University | And 4 more authors.
International Journal of Molecular Sciences | Year: 2011

Tryptanthrin, a kind of indole quinazoline alkaloid, has been shown to exhibit anti-microbial, anti-inflammation and anti-tumor effects both in vivo and in vitro. However, its biological activity on human chronic myeloid leukemia cell line K562 is not fully understood. In the present study, we investigated the proliferation-attenuating and apoptosis-inducing effects of tryptanthrin on leukemia K562 cells in vitro and explored the underlying mechanisms. The results showed that tryptanthrin could significantly inhibit K562 cells proliferation in a time- and dose-dependent manner as evidenced by MTT assay and flow cytometry analysis. We also observed pyknosis, chromatin margination and the formation of apoptotic bodies in the presence of tryptanthrin under the electron microscope. Nuclei fragmentation and condensation by Hoechst 33258 staining were detected as well. The amount of apoptotic cells significantly increased whereas the mitochondrial membrane potential decreased dramatically after tryptanthrin exposure. K562 cells in the tryptanthrin treated group exhibited an increase in cytosol cyt-c, Bax and activated caspase-3 expression while a decrease in Bcl-2, mito cyt-c and pro-caspase-3 contents. However, the changes of pro-caspase-3 and activated caspase-3 could be abolished by a pan-caspase inhibitor ZVAD-FMK. These results suggest that tryptanthrin has proliferation-attenuating and apoptosis-inducing effects on K562 cells. The underlying mechanism is probably attributed to the reduction in mitochondria membrane potential, the release of mito cyt-c and pro-caspase-3 activation. © 2011 by the authors; licensee MDPI, Basel, Switzerland.

Lee M.-H.,Seoul National University | Na H.,Seoul National University | Kim E.-J.,Seoul National University | Lee H.-W.,Laboratory Animal Research Center | Lee M.-O.,Seoul National University
Oncogene | Year: 2012

The metastasis-associated protein 1 (MTA1) is overexpressed in various human cancers and is closely connected with aggressive phenotypes; however, little is known about the transcriptional regulation of the MTA1 gene. This study identified the MTA1 gene as a target of p53-mediated transrepression. The MTA1 promoter contains two putative p53 response elements (p53REs), which were repressed by the p53-inducing drug 5-fluorouracil (5-FU). Notably, 5-FU treatment decreased MTA1 expression only in p53 wild-type cells. p53 and histone deacetylases 1/2 were recruited, and acetylation of H3K9 was decreased on the promoter region including the p53REs after 5-FU treatment. Proteomics analysis of the p53 repressor complex, which was pulled down by the MTA1 promoter, revealed that the poly(ADP-ribose) polymerase 1 (PARP-1) was part of the complex. Interestingly, p53 was poly(ADP-ribose)ylated by PARP-1, and the p53-mediated transrepression of the MTA1 gene required poly(ADP-ribose)ylation of p53. In summary, we report a novel function for poly(ADP-ribose)ylation of p53 in the gene-specific regulation of the transcriptional mode of p53 on the promoter of MTA1. © 2012 Macmillan Publishers Limited All rights reserved.

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