Abstract
About 50% of human cancers across the globe arise due to a mutation in the p53 gene which gives rise to its functional inactive form, and in the rest of the cancer the efficacy of active p53 (wild-type) is hindered by MDM2-mediated degradation. Breakdown of the p53-MDM2 association may constitute an effective strategy to stimulate or reinstate the activity of wild type p53, thereby reviving the p53 tumor suppressor capability. S100A1 has been revealed to associate with the N-terminal domain of MDM2 and p53 protein. We utilized NMR spectroscopy to study the interface amongst the S100A1 and N-terminal domain of MDM2. Additionally, the S100A1-MDM2 complex generated through the HADDOCK program was then superimposed with the p53 (peptide) -MDM2 complex reported earlier. The overlay indicated that a segment of S100A1 could block the interaction of p53 (peptide) -MDM2 complex significantly. To further justify our assumption, we performed HSQC-NMR titration for the S100A1 and p53 N-terminal domain (p53-TAD). The data obtained indicated that the S100A1 segment comprising nearly 17 residues have some common residues that interact with both MDM2 and p53-TAD. Further, we synthesized the 17-residue peptide derived from the S100A1 protein and attached it to the cell-penetrating HIV-TAT peptide. The HSQC-NMR competitive binding experiment revealed that Peptide 1 could successfully interfere with the p53-MDM2 interaction. Furthermore, functional effects of the peptide was validated in cancer cells. The results showed that Peptide 1 effectively inhibited cell proliferation, and increased the protein levels of p53 and its downstream p21 in MCF-7 cells. Treatment of Peptide 1 resulted in cell cycle arrest at G2/M phase, and also induced apoptotic cell death at higher concentration. Taken together, the results suggest that disruption of the interaction of p53 and MDM2 by Peptide 1 could activate normal p53 functions, leading to cell cycle arrest and apoptotic cell death in cancer cells. We proposed here that S100A1 could influence the p53-MDM2 interaction credibly and possibly reactivates the wild type p53 pathway.
Highlights
The p53 protein is widely known as the “guardian of the genome” pertaining to its ability to inhibit tumor development. [1] In response to numerous cellular stressors, p53 acts as a tumor suppressor by precisely controlling its transcription activity
We studied the interaction of S100A1 protein to the N- terminal domain of MDM2 and p53 N-terminal domain (p53-TAD) by employing the NMR experiments
This manifestation was due to 15N nuclei being closer to the interface section of the proteins flanked by S100A1 and MDM2
Summary
The p53 protein is widely known as the “guardian of the genome” pertaining to its ability to inhibit tumor development. [1] In response to numerous cellular stressors, p53 acts as a tumor suppressor by precisely controlling its transcription activity. [1] In response to numerous cellular stressors, p53 acts as a tumor suppressor by precisely controlling its transcription activity. It regulates the expression of downstream specific genes whose protein output plays role in cell growth arrest, senescence, or programmed cell death, thereby prohibiting oncogenesis. The level of p53 activity is meticulously monitored by MDM2, and the p53-MDM2 interaction forms a negative feedback loop or self-regulating response loop that confines the growth suppressing action of p53. As a controller of the p53 tumor suppressor role, MDM2, once expressed in excess amount, is tumorigenic in nature. [35, 36]
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