Design,Synthesis And Properties Of Benzoylated Peptides Based On BRCA 1(854-871)

Breast cancer has the highest morbidity and relatively high mortality among female malignant tumors in the world,which seriously endangers women’s health.Chemotherapy and radiotherapy are two commonly used treatments for breast cancer,mainly by affecting the cell cycle by damaging the DNA double strands of cancer cells,thereby killing cancer cells.However,RAD51 protein is overexpressed in breast cancer patients,which will enhance the homologous recombination(HR)ability of cancer cells,and then accelerate the repair of damaged DNA double strand,resulting in drug resistance.However,there is an overexpression of RAD51 protein in breast cancer patients,which will enhance the homologous recombination(HR)ability of cancer cells,and then accelerate the repair of damaged DNA double strand,resulting in drug resistance of cells.The study found that breast cancer 1(BRCA1)is closely related to breast cancer,and can combine with RAD51 protein to regulate HR process and participate in the repair of damaged DNA.In this paper,on the premise of retaining the five active sites in the BRCA1 gene,the truncated peptide BRCA1(854-871),which has a strong effect on the RAD51 protein,was selected as the parent peptide.Nine benzoylated peptides containing benzoamide pharmacophore were obtained by coupling the N-terminus of BRCA 1(854-871)with nine precursor molecules of anti cancer effect.Two important sequences of RAD51 protein are target peptides,namely RAD51(158-180)and RAD51(181-200).All polypeptides were synthesized by solid-phase Fmoc method,purified by reversed-phase high performance liquid chromatography(RP-HPLC),and characterized by electrospray ionization mass spectrometry(ESI-MS),and the final purity was above 95%.The interaction of parent peptide BRCA1(854-871)and its benzoylated peptide and RAD51 target peptide was investigated by fluorescence spectroscopy and circular dichroism(CD).In addition,the toxicity of parent peptide BRCA 1(854-871)and its benzoylated peptide to cancer cells was studied using cytotoxicity assay.Fluorescence analysis showed that both the parent peptide(854-871)and any benzoylated peptide could bind to the two RAD51 target peptides,resulting in static fluorescence quenching,but the binding ability was different.Among them,P3 has the strongest binding ability to target peptides RAD51(158-180)and RAD51(181-200),with binding constants of 7.59×104 M-1 and 1.52×104 M-1,respectively,followed by P9.Circular dichroism analysis showed that the secondary structure of two RAD51 target peptides could be changed by both the parent peptide(854-871)and any benzoylated peptide.Among them,P3 had the greatest effect on the α-helix of target peptides RAD51(158-180)and RAD51(181-200),which were 24.1%～37.9%and 22.7%～31.9%,respectively,followed by P9,which was consistent with the fluorescence results.The results of cytotoxicity experiments showed that P3、P5 and P6 were more toxic to breast cancer cells,and the cell survival rates were 53.4%、51.2%and 54.3%,respectively.Combined with the results of double spectrum analysis and cytotoxicity experiments,P3 is most likely to act as an inhibitor of RAD51,which provides a research idea for the development of polypeptide drugs for breast cancer.