Influence Of Magnesium Ion On The P53-DNA Binding By Atomic Force Microscopy

In the present case, Cancer (Tumor) is one of the diseases threating human health seriously. Its occurrence is related with unrepaired damaging-DNA replication, unlimited cell cycle or apoptosis in the DNA replication process. However, protein p53 can recognize and repair damaging-DNA in numerous studies, so that it can suppress tumor occurrence. And, it has been founded in a large number of human cancer cells. Thus, p53 is also called anti-tumor protein or tumor suppressor protein that plays a significant role in apoptosis, preserving genomic stability and preventing oncogene expression. Besides, the processes of DNA transcription and expression involve in the interaction of protein and DNA in living cells. And, tumor suppressor protein p53 is a key protein involved in the cell replication process. For the reasons, there is an important significance for fundamental research on tumor suppressor protein p53 and DNA interaction. It is an advantage to make sense of the mechanism of p53 and DNA interaction, especially. Therefore, we further investigate the full length human p53 protein and double-stranded DNA interaction in vitro.Here, we use atomic force microscopy (AFM) imaging at the single-molecule level and obtain the quantities of p53 adhering to 20000bp DNA in statistics. We report a fact that the number of p53 adhering to DNA will be elevated as the increasing concentration ratios of p53-DNA. According to the consequence in statistics, we measure the dissociation constant of p53-DNA binding by least square method. In physiological condition, the dissociation constant is 328.02 nmol/L.Meanwhile, we demonstrate the consequence of p53-DNA binding with 5000bp DNA. Then, we investigate that there is an effect on counter ion such as magnesium in buffer to the number of p53 adhering to DNA.Xizeng Feng et al. have found that the Mg2+ significantly stimulated the binding of the protein to DNA in a sequence-independent manner, which differes from that of zinc ions in a sequence-specific manner. In the mean while, the high concentration of magnesium ions can promote p53 aggregation and p53-DNA self-assembly networks occurrence.Meanwhile, we have proposed a model to explain it. It is an advantage to make sense of the mechanism and function on protein p53, as well as for cancer therapy, cancer drug development and cancer detection methods.