Design,Synthesis Based Of BRCA1^856-871 Modified By Nicotinic Acid And Its Derivatives And Interaction With The Target Of RAD51

Breast cancer is the disease with the highest incidence and death rate among female malignant tumors.The occurrence of breast cancer is related to a variety of causes,among which genetic family history is one of the main risk factors.In addition,it is also related to radiation exposure and taking estrogen.It is found that the breast cancer susceptibility gene BRCA1 mutant breast cancer are closely related.The BRCA1 gene has a RAD51 binding region,and BRCA1846-871 is one of the conserved sequences.BRCA1 cooperates with the RAD51 protein to maintain the n ormal growth and differentiation process of cells,repairing the damage of DNA genetic material and protecting the integrity of genes.When the RAD51 protein is overexpressed in the human body,it will accelerate the growth and spread of cancer cells and increase the resistance.of cancer cells.In this paper,the conservative sequence of BRCA1(amino acid code is 846-871)was used as a template,and it was truncated while retaining 5 active sites of mutations.With BRCA1856-871 as the parent peptide,8 different kinds of small molecule drugs with niacinamide pharmacophore with different anticancer effects were coupled.RAD51158-180 and RAD51181-200 were used as targets.Solid phase synthesis using Fmoc synthesis of all peptides,high performance liquid chromatography for separation and purification.Then ESI-MS electrospray mass spectrometry was used for characterization,and the target peptides with purity above 90%were obtained.Fluorescence spectroscopy and circular dichroism spectroscopy were used to analyze the interaction of BRCA1856-871 modified by nicotinamide pharmacophore with target peptide RAD51.In addition,cytotoxicity experiments were carried out on the nicotinamidated peptide with better interaction.Fluorescence spectroscopy data shows that after adding any nicotinamidated peptide,most of them will have different degrees of fluorescence quenching,which can be calculated as static quenching.The circular dichroism data shows that after adding any nicotinamidated peptide,it has different degrees of influence on the secondary structure of the target RAD51.Comprehensively,all nicotinamidated peptide can interact with RAD51,but their binding ability is different.Among them,the BRCA1856-871 peptide coupled with 2-(trifluoromethyl)nicotinic acid has the strongest affinity with RAD51158-180 and RAD51181-200.with a binding constant of 4.09 ×104 L·mol-1 and 4.31 ×104 L·mol-1.Finally,through the cytotoxicity test,the lethal effect of the sample peptide on breast cancer cells was detected and compared with the parent peptide.It is concluded that the BRCA1856-871 peptide coupled with 2-(trifluoromethyl)nicotinic acid has the relatively greatest lethality to MDA-MB-231 cells,which is consistent with the predicted results.