DNA Damage-induced Expression of p53 Suppresses Mitotic Checkpoint Kinase hMps1: THE LACK OF THIS SUPPRESSION IN p53MUT CELLS CONTRIBUTES TO APOPTOSIS

Mandar R Bhonde,Marie-Luise Hanski,Jan Budczies,Minh Cao,Bernd Gillissen,Dhatchana Moorthy,Federico Simonetta,Hans Scherübl,Matthias Truss,Christian Hagemeier,Hans-Werner Mewes,Peter T Daniel,Martin Zeitz,Christoph Hanski

doi:10.1074/jbc.m511333200

Abstract

DNA damage induced by the topoisomerase I inhibitor irinotecan (CPT-11) triggers in p53(WT) colorectal carcinoma cells a long term cell cycle arrest and in p53MUT cells a transient arrest followed by apoptosis (Magrini, R., Bhonde, M. R., Hanski, M. L., Notter, M., Scherübl, H., Boland, C. R., Zeitz, M., and Hanski, C. (2002) Int. J. Cancer 101, 23-31; Bhonde, M. R., Hanski, M. L., Notter, M., Gillissen, B. F., Daniel, P. T., Zeitz, M., and Hanski, C. (2006) Oncogene 25, 165-175). The mechanism of the p53-independent apoptosis still remains largely unclear. Here we used five p53WT and five p53MUT established colon carcinoma cell lines to identify gene expression alterations associated with apoptosis in p53MUT cells after treatment with SN-38, the irinotecan metabolite. After treatment, 16 mitosis-related genes were found to be expressed at least 2-fold stronger in the apoptosis-executing p53MUT cells than in the cell cycle-arrested p53WT cells by oligonucleotide microarray analysis. One of the genes whose strong post-treatment expression was associated with apoptosis was the mitotic checkpoint kinase hMps1 (human ortholog of the yeast monopolar spindle 1 kinase). hMps1 mRNA and protein expression were suppressed by the treatment-induced and by the exogenous adenovirus-coded p53 protein. The direct suppression of hMps1 on RNA level or inhibition of its activity by a dominant-negative hMps1 partly suppressed apoptosis. Together, these data indicate that the high expression of mitotic genes in p53MUT cells after SN-38 treatment contributes to DNA damage-induced apoptosis, whereas their suppression in p53WT cells acts as a safeguard mechanism preventing mitosis initiation and the subsequent apoptosis. hMps1 kinase is one of the mitotic checkpoint proteins whose expression after DNA damage in p53MUT cells activates the checkpoint and contributes to apoptosis.

Highlights

The function of p53 protein as a guardian of the genome is to prevent the organism from propagation of potentially harmful DNA lesions
The direct suppression of hMps1 on RNA level or inhibition of its activity by a dominant-negative hMps1 partly suppressed apoptosis. These data indicate that the high expression of mitotic genes in p53MUT cells after SN-38 treatment contributes to DNA damageinduced apoptosis, whereas their suppression in p53WT cells acts as a safeguard mechanism preventing mitosis initiation and the subsequent apoptosis. hMps1 kinase is one of the mitotic checkpoint proteins whose expression after DNA damage in p53 MUT cells activates the checkpoint and contributes to apoptosis
We showed previously that despite this general concept, colon carcinoma cells may respond differently to the chemotherapeutic irinotecan (CPT-11); the p53WT cells execute a long term cell cycle arrest after irinotecan treatment, whereas the p53-deficient cells perform a transient cell cycle arrest followed by apoptosis [1]

Summary

Introduction

The function of p53 protein as a guardian of the genome is to prevent the organism from propagation of potentially harmful DNA lesions. These data indicate that the high expression of mitotic genes in p53MUT cells after SN-38 treatment contributes to DNA damageinduced apoptosis, whereas their suppression in p53WT cells acts as a safeguard mechanism preventing mitosis initiation and the subsequent apoptosis. HMps1 kinase is one of the mitotic checkpoint proteins whose expression after DNA damage in p53 MUT cells activates the checkpoint and contributes to apoptosis.

Results

Conclusion