Mimotopes and proteome analyses using human genomic and cDNA epitope phage display

Area of Science:

• Molecular Biology
• Genomics
• Biotechnology

Background:

• Post-genomic era necessitates protein-based strategies for gene target validation.
• Phage display is a key technology for defining protein-protein interactions and generating peptide binders.
• Epitope phage display libraries offer potential for enriching coding exon sequences from genomic loci.

Purpose of the Study:

• To evaluate genomic and cDNA phage display strategies for identifying genes.
• To enrich cell surface receptor tyrosine kinase genes from a breast cancer cDNA library.
• To investigate the role of bacterial DNA as mimotopes in phage display selection.

Main Methods:

• Construction and selection of a genomic phage display library (2 x 10^6 clones) using antibodies against Interleukin-4 (IL-4) and Interleukin-13.
• Screening of a breast cancer cDNA phage display library against an anti-erbB2 monoclonal antibody.
• DNA sequencing and competition ELISA for clone characterization and specificity confirmation.

Main Results:

• Significant enrichment of the genomic library after two selection rounds.
• Identification of bacterial (E. coli) DNA sequences acting as mimotopes, competing with target epitopes.
• Confirmation of mimotope specificity for IL-4 and selection of mimotopes for a receptor tyrosine kinase gene.

Conclusions:

• Mimotope identification is crucial for phage display-based protein validation and two-hybrid assays.
• The E. coli genome can serve as a source of peptide diversity biased towards protein-coding sequences.
• Phage display strategies require careful consideration of bacterial DNA interference for accurate target identification.