Menage a Trois 1-Mediated p53 Ubiqutin Degradation Promotes Colorectal Cancer Malignance

Abstract

Background MNAT1 (menage a trois 1, MAT1), a cyclin-dependent kinase-activating kinase (CAK) complex, high expresses in various cancers and is involved in cancer pathogenesis. However, mechanisms underlying its regulation in carcinogenesis are unclear. Methods Colorectal cancer (CRC) tissue microarray was used to evaluate MNAT1 expressions using immunohistchemistry, MNAT1 in CRC cell lines was detected using Western-blotting. Growths of the cells tansfected with MNAT1 or shMNAT1 were observed using MTT and colony formation. Affects of MNAT1 on p53/TP53 expressions were analyzed using Western-blotting and Real-time PCR. Immunoprecipitation assay was used to analyze interaction p53 with MNAT1, p53 downstream molecules were detected. The apoptosis of CRC cells with MNAT1 or shMNAT1 was analyzed using flow cytometry. BABL/c nude mice were used to observe effects of MNAT1 on CRC cell growth in vivo. Findings MNAT1 was highly expressed in CRC tissues and cells, and MNAT1 expressions were associated with CRC carcinogenesis and poor patient outcomes. MNAT1-knockin increased CRC cell growth and colony formation, and MNAT1-knockdown decreased cell growth, motility and invasion. MNAT1 physically interacted with p53, MNAT1 also increased interaction of MDM2 with p53. Strikingly, MNAT1 mediates p53 ubiquitin-degradation. MNAT1 shortened p53 half-life. Moreover, MNAT1 induced RAD51 and reduced PARP and BAX expression through p53, and inhibited CRC cell apoptosis. MANT1 promoted tumor growths in nude mice following decreased p53. Interpretation MNAT1 binds to p53, mediates p53 ubiquitin-degradation through MDM2, increases CRC cell growth and decreases apoptosis, and finally promotes CRC malignance. Funding: National Natural Science Foundation of China (81372282, 81402265, 81502346). Declaration of Interest: None. Ethical Approval: All procedures were consistent with the National Institutes of Health Guide and approved by institutional board with patients’ written consent. This study was evaluated and approved by the Ethics Committee of the Affiliated Cancer Hospital of Xiangya Medical School, Central South University. All animal experiments were performed according to the National Institutes of Health Animal Use Guidelines on the Use of Experimental Animals.