p73 is a structural and functional homologue of the p53 tumor-suppressor protein. Like p53, p73 is activated in response to DNA-damaging insults to induce cell cycle arrest or apoptosis. Under these conditions p73 is tyrosine-phosphorylated by c-Abl, a prerequisite modification for p73 to elicit cell death in fibroblasts. In this study we report that in response to ionizing radiation, p73 undergoes nuclear redistribution and becomes associated with the nuclear matrix. This association is c-Abl-dependent because it was not observed in cells that are defective in c-Abl kinase activation. Moreover, STI-571, a specific c-Abl kinase inhibitor, is sufficient to block significantly p73 alpha nuclear matrix association. The observed c-Abl dependence of nuclear matrix association was recapitulated in the heterologous baculovirus system. Under these conditions p73 alpha but not p53 is specifically tyrosine-phosphorylated by c-Abl. Moreover, the phosphorylated p73 alpha is predominantly found in association with the nuclear matrix. Thus, in response to ionizing radiation p73 is modified in a c-Abl-dependent manner and undergoes nuclear redistribution and translocates to associate with the nuclear matrix. Our data describe a novel mechanism of p73 regulation.
"Initial studies demonstrated that c-Abl is associated with p73 through SH3 domain of c- Abl and PY motif of p73, and directly phosphorylates p73 at Tyr-99 in response to CDDP and ionizing radiation   . Phosphorylated form of p73 underwent nuclear redistribution and became associated with the nuclear matrix . c-Abl-mediated phosphorylation of p73 at Tyr-99 increased its stability and enhanced its transcriptional as well as proapoptotic activity. "
[Show abstract][Hide abstract] ABSTRACT: p73 is one of the tumor-suppressor p53 family of nuclear transcription factor. As expected from the structural similarity between p53 and p73, p73 has a tumor-suppressive function. However, p73 was rarely mutated in human primary tumors. Under normal physiological conditions, p73 is kept at an extremely low level to allow cells normal growth. In response to a certain subset of DNA damages, p73 is induced dramatically and transactivates an overlapping set of p53-target genes implicated in the promotion of cell cycle arrest and/or apoptotic cell death. Cells undergo cell cycle arrest and/or apoptotic cell death depending on the type and strength of DNA damages. p73 is regulated largely through the posttranslational modifications such as phosphorylation and acetylation. These chemical modifications are tightly linked to direct protein-protein interactions. In the present paper, the authors describe the functional significance of the protein-protein interactions in the regulation of proapoptotic p73.
[Show abstract][Hide abstract] ABSTRACT: Advances in our understanding of the mechanisms by which tumor cells detect drug-induced DNA damage leading to apoptotic death have aided in the design of novel, potentially more selective strategies for cancer treatment. Several of these strategies use proapoptotic factors and have shown promise in sensitizing tumor cells to the cytotoxic actions of traditional cancer chemotherapeutic drugs. Although antiapoptotic factors are generally regarded as poor prognostic factors for successful cancer chemotherapy, strategies that use antiapoptotic factors in combination with suicide or other gene therapies can also be considered. The introduction of antiapoptotic factors that act downstream of drug-induced mitochondrial transition delays, but does not block, the ultimate cytotoxic response to cancer chemotherapeutic drugs that activate a mitochondrial pathway of cell death. Recent studies using the cytochrome P-450 prodrug cyclophosphamide exemplify how the antiapoptotic, caspase-inhibitory baculovirus protein p35 can be combined with P-450 gene-directed enzyme prodrug therapy to prolong localized, intratumoral production of cytotoxic drug metabolites without inducing tumor cell drug resistance. This model may be adapted to other gene therapies, including those that target death receptor pathways, to maximize the production of soluble, bystander cytotoxic factors and prodrug metabolites and thereby amplify the therapeutic response.
Cancer Research 01/2004; 63(24):8563-72. · 9.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The nuclear matrix (NM) is the structural framework of the nucleus that consists of the peripheral lamins and pore complexes, an internal ribonucleic protein network, and residual nucleoli. Differences between the nuclear matrix protein (NMP) composition of transformed cells and their normal homologues were detected in numerous cases. Actually several tumor-specific nuclear matrix proteins (NMPs) are proposed for diagnostic of bladder, breast, colon and some other cancers. According to the role of NMPs in development and phenotype of a given neoplasms the tumors can be classified as follows: I. Tumors bearing mutations in the genes encoding NMPs. The group consists of following subgroups: 1) hereditary cancer syndromes with mutations in the NM-attached oncoproteins or tumor suppressor genes; 2) sporadic tumors with somatic mutations in the NM-attached oncoproteins, tumor suppressor genes or replication enzymes; 3) leukemias with fused NMPs. II. Tumors with phenotypic quantitative or qualitative changes of the NMP spectrum.
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