The main application of the yeast two-hybrid system is the rapid and direct analysis of interactions between known proteins and the isolation of new ligands that interact with known proteins and their coding genes. The yeast two-hybrid system has the following advantages for detecting interactions between proteins: ⑴ The action signal is given by reconstructing the action of the transcription factor in the cell after the fusion gene is expressed, eliminating the tedious steps of purifying the protein. ⑵ The detection is carried out in living cells and can represent the true situation inside the cells to a certain extent. ⑶ The result of the detection can be the cumulative effect of gene expression products, so weak or temporary interactions that exist between proteins can be detected. ⑷The yeast two-hybrid system can use materials from different tissues, organs, cell types and differentiation stages to construct cDNA libraries, and can analyze proteins in a variety of different subcellular parts and functions such as cytoplasm, nucleus and membrane-bound proteins. For example, it has been reported that the interactions between RAP1 and RIF1ii, P21cip1 and CDK2iii, p16 and CDK4iv, etc. were successfully analyzed.