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Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73
BACKGROUND: TAp73, a member of the p53 tumor suppressor family, is frequently overexpressed in malignant tumors in humans. TAp73 abundance and phosphorylation modification result in variations in transcriptional activity. In a previous study, we found that the antitumor function of TAp73 was reactiv...
Autores principales: | , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Dove Medical Press
2015
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4662374/ https://www.ncbi.nlm.nih.gov/pubmed/26640387 http://dx.doi.org/10.2147/OTT.S90302 |
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author | Hu, ZhengBo Xu, ZunYing Liao, XiaoHong Yang, Xiao Dong, Cao Luk, KuaDi Jin, AnMin Lu, Hai |
author_facet | Hu, ZhengBo Xu, ZunYing Liao, XiaoHong Yang, Xiao Dong, Cao Luk, KuaDi Jin, AnMin Lu, Hai |
author_sort | Hu, ZhengBo |
collection | PubMed |
description | BACKGROUND: TAp73, a member of the p53 tumor suppressor family, is frequently overexpressed in malignant tumors in humans. TAp73 abundance and phosphorylation modification result in variations in transcriptional activity. In a previous study, we found that the antitumor function of TAp73 was reactivated by dephosphorylation in head and neck squamous cell carcinomas. Polo-like kinase 2 (PLK2) displayed a close relationship with the p53 family in affecting the fate of cells. Herein, we investigate the hypothesis that PLK2 phosphorylates TAp73 and inhibits TAp73 function. MATERIALS AND METHODS: Head and neck squamous cell carcinoma cell lines and osteosarcoma cell lines were used as natural models of the different expression levels of TAp73. Phosphorylation predictor software Scansite 3.0 and the predictor GPS-polo 1.0 were used to analyze the phosphorylation sites. Coimmunoprecipitation, phosphor-tag Western blot, metabolic labeling, and indirect immunofluorescence assays were used to determine the interactions between PLK2 and TAp73. TAp73 activity was assessed by Western blot and reverse transcription polymerase chain reaction, which we used to detect P21 and PUMA, both downstream genes of TAp73. The physiological effects of PLK2 cross talk with TAp73 on cell cycle progress and apoptosis were observed by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assays. RESULTS: PLK2 binds to and phosphorylates TAp73. PLK2 phosphorylates TAp73 at residue Ser48 and prohibits TAp73 translocation to the nucleus. Additionally, PLK2 inhibition combined with a DNA-damaging drug upregulated p21 and PUMA mRNA expression to a greater extent than DNA-damaging drug treatment alone. Inhibiting PLK2 in TAp73-enriched cells strengthened the effects of the DNA-damaging drug on both G1 phase arrest and apoptosis. Pretreatment with TAp73-siRNA weakened these effects. CONCLUSION: These findings reveal a novel PLK2 function (catalyzed phosphorylation of TAp73) which suppresses TAp73 functions. PLK2 promotes the survival of human tumor cells, a novel insight into the workings of malignant tumors characterized by TAp73 overexpression, and one that could speed the development of therapies. |
format | Online Article Text |
id | pubmed-4662374 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | Dove Medical Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-46623742015-12-04 Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73 Hu, ZhengBo Xu, ZunYing Liao, XiaoHong Yang, Xiao Dong, Cao Luk, KuaDi Jin, AnMin Lu, Hai Onco Targets Ther Original Research BACKGROUND: TAp73, a member of the p53 tumor suppressor family, is frequently overexpressed in malignant tumors in humans. TAp73 abundance and phosphorylation modification result in variations in transcriptional activity. In a previous study, we found that the antitumor function of TAp73 was reactivated by dephosphorylation in head and neck squamous cell carcinomas. Polo-like kinase 2 (PLK2) displayed a close relationship with the p53 family in affecting the fate of cells. Herein, we investigate the hypothesis that PLK2 phosphorylates TAp73 and inhibits TAp73 function. MATERIALS AND METHODS: Head and neck squamous cell carcinoma cell lines and osteosarcoma cell lines were used as natural models of the different expression levels of TAp73. Phosphorylation predictor software Scansite 3.0 and the predictor GPS-polo 1.0 were used to analyze the phosphorylation sites. Coimmunoprecipitation, phosphor-tag Western blot, metabolic labeling, and indirect immunofluorescence assays were used to determine the interactions between PLK2 and TAp73. TAp73 activity was assessed by Western blot and reverse transcription polymerase chain reaction, which we used to detect P21 and PUMA, both downstream genes of TAp73. The physiological effects of PLK2 cross talk with TAp73 on cell cycle progress and apoptosis were observed by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assays. RESULTS: PLK2 binds to and phosphorylates TAp73. PLK2 phosphorylates TAp73 at residue Ser48 and prohibits TAp73 translocation to the nucleus. Additionally, PLK2 inhibition combined with a DNA-damaging drug upregulated p21 and PUMA mRNA expression to a greater extent than DNA-damaging drug treatment alone. Inhibiting PLK2 in TAp73-enriched cells strengthened the effects of the DNA-damaging drug on both G1 phase arrest and apoptosis. Pretreatment with TAp73-siRNA weakened these effects. CONCLUSION: These findings reveal a novel PLK2 function (catalyzed phosphorylation of TAp73) which suppresses TAp73 functions. PLK2 promotes the survival of human tumor cells, a novel insight into the workings of malignant tumors characterized by TAp73 overexpression, and one that could speed the development of therapies. Dove Medical Press 2015-11-20 /pmc/articles/PMC4662374/ /pubmed/26640387 http://dx.doi.org/10.2147/OTT.S90302 Text en © 2015 Hu et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. |
spellingShingle | Original Research Hu, ZhengBo Xu, ZunYing Liao, XiaoHong Yang, Xiao Dong, Cao Luk, KuaDi Jin, AnMin Lu, Hai Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73 |
title | Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73 |
title_full | Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73 |
title_fullStr | Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73 |
title_full_unstemmed | Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73 |
title_short | Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73 |
title_sort | polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of tap73 |
topic | Original Research |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4662374/ https://www.ncbi.nlm.nih.gov/pubmed/26640387 http://dx.doi.org/10.2147/OTT.S90302 |
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