Isolation, characterization and functional analysis of full length p53 cDNA from Bubalus bubalis

miR-488-5p promotes esophageal squamous cell carcinoma progression by suppressing the P53 pathway

Background

miR-488-3p has been reported to play an important role in cancer progression and metastasis. The protein 53 (P53) gene serves as a mediator and biomarker of esophageal squamous cell carcinoma (ESCC). However, the molecular mechanism underlying miR-488-5p in the pathology of ESCC through the P53 pathway has not been examined.

Methods

The expression levels of miR-488-5p were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Cytological experiments were performed to evaluate the biological functions of miR-488-5p. A bioinformatics analysis was performed to determine the pathways and key miR-488-5p targets associated with ESCC. Correlations between miR-488-5p and P53 signaling pathways were validated by western blotting and the dual luciferase reporter gene system. Finally, the expression level of miR-488-5p was regulated and tumor formation experiments were performed in nude mice.

Results

The qRT-PCR analysis showed that MiR-488-5p expression was more upregulated in the KYSE-150 group than the HEEC group. In the KYSE-150 cells, the colony formation assay and flow cytometry analysis indicated that the miR-488-5p inhibitor inhibited cell viability and increased cell apoptosis; however, these effects were recovered by P53 knockdown (KD). In addition, cell invasion and cell migration were inhibited by the miR-488-5p inhibitor, but were also improved by P53 KD. Similarly, the miR-488-5p inhibitor induced the expression of P53 and P21 than normal control (NC) group in which miR-488-5p expression was normal, while P53 KD prevented the effects of the miR-488-5p inhibitor in KYSE-150 cells. Additionally, we found that tumor size was obviously smaller in miR-488-5p overexpression (OE)+ P53 OE mice than miR-488-5p OE mice. Hematoxylin and eosin and immunohistochemistry staining also revealed similar results.

Conclusions

Our results suggest that miR-488-5p promotes ESCC progression by suppressing the P53 pathway. These findings should provide novel ideas for ESCC therapies.

C-terminal region of human p53 attenuates buffalo p53 N-terminal-specific transactivation of p21 promoter by modulating tetramerization of the protein

Here, we have studied in p53 null H1299 lung carcinoma cells, the dominant-negative effect of human p53 (h-p53) on buffalo p53 (b-p53) induced nuclear transactivation-dependent function. Recently, we have isolated and cloned the full-length cDNA of buffalo p53. Buffalo and human p53 proteins exhibit a high degree of structural and functional similarities. In transiently transfected H1299 cell line b-p53 appeared to be more sensitive to Mdm2-mediated degradation as compared to h-p53, although its ability to transactivate p21 promoter was stronger than that of the human counterpart. This higher transactivation ability of b-p53 was lost in the presence of h-p53 suggesting, a dominant-negative effect of h-p53 on b-p53's transactivation of p21 promoter. Both human and buffalo p53 proteins could hetero-oligomerize but the b-p53 could tetramerize much faster than the h-p53. A chimeric cDNA construct of human p53 was made where the 1-260 bp N-terminus was replaced with buffalo p53 counterpart and expressed in H1299 cell line. The tetramerization ability of the chimeric p53 protein was comparable to that of h-p53. Properties of b-p53 like stronger p21 transactivation and super sensitivity to Mdm2 mediated degradation were lacking in the chimeric protein. Thus, it is suggested that faster ability of tetramerization as well as higher transactivation property of buffalo p53 is determined by the interplay of N- and C-terminal domains through macromolecular interactions.