In vivo production of cyclic peptides for inhibiting protein-protein interaction

A method comprising:

• a) introducing a library of fusion nucleic acids into a plurality of cells, wherein said cells comprise a first interacting protein and a second interacting protein and wherein said library of fusion nucleic acids comprises, from 5′ to 3′:
• i) nucleic acid encoding a C-terminal intein motif;
• ii) nucleic acid encoding a peptide;
• and
• iii) nucleic acid encoding an N-terminal intein motif;
• wherein said introducing provides for production of a cyclic peptide in said cells;
• and;
• b) identifying a cell comprising a cyclic peptide capable of preventing interaction of said interacting proteins.