Synthesis And Interaction Of RAD51(231-260) With Analog-BRC4Peptides

Breast cancer represents one of the most common causes of cancer-associatedfemale health in the world today. The breast cancer suppressor protein, BRCA2, isessential in vivo for RAD51-mediated HDR. The BRCA2contains eight conservedsequence motifs-the BRC repeats. The BRC repeats appear to be the primary locus forthe BRCA2-RAD51interaction. The human RAD51protein (HsRad51) and BRCA2are crucial for DNA repair processes that are based on homologous recombination, soit is very important to study the interaction of the BRC repeats and RAD51, the studyon BRC repeats-RAD51interaction will provide supports for understanding themechanism of breast cancer and make a positive significance in treatment of Breastcancer and human health.In this research, the RAD51(231-260) was selected as the target peptide, theBRC4was selected as the template. According to the structure characteristics ofBRC4peptide and the eight conserved sequence:-------F-TASGK-(I/V)-(I/V)S---L-K----(L/F)-(D/E)---, the two analog-BRC4peptides(analog-BRC4-1peptide:FEPTLLGFHTASGKKVKIAKESLDKVKNLFDEKEQ, analog-BRC4-2peptide:KEPTLLGFHTASGKKV KIAKESLDKVKNWFDEKEQ) were designed. These peptideswere synthesized by Fmoc solid-phase synthesis and fragment condensation. Thesepeptides were isolated and Purified by RP-HPLC, and charactered by ESI-MS.The interaction of BRC4and the two analog-BRC4peptides with RAD51(231-260) had been investigated by using fluorescence spectroscopy and circulardichroism spectrum. The results showed that: the fluorescence intensity of RAD51(231-260) decreased with the increasing of BRC4and the the twoanalog-BRC4peptides (analog-BRC4-1peptide, analog-BRC4-2peptide). Thequenched intensity of fluorescence caused by analog-BRC4-1peptide, analog-BRC4-2peptide and BRC4were different. With adding BRC4and its two analog-BRC4peptides, CD spectrum showed that the secondary structure of RAD51(231-260)changed. With adding BRC4and its two analog-BRC4peptides, the alpha helixproportion of RAD51(231-260) rised, and the corresponding CD map showed a blue-shift phenomenon. The blue-shift phenomenon caused by analog-BRC4-2peptide was bigger than the shift caused by BRC4. Combining with the results offluorescence spectroscopy and circular dichroism spectrum, the results showed thatthe interaction of RAD51(231-260) and two designed analog-BRC4peptidesstrengthened when Lys and Leu of BRC4were replaced by Phe and Trp. In theinteraction of RAD51(231-260) and two designed analog-BRC4peptides, theanalog-BRC4-1peptide played the important role.