Screening and Identification of Peptides that Bind Specifically to the X gene Promoter of Hepatitis B Virus Using a Combinatorial Peptide Library Approach

Hepatitis B virus (HBV) X protein (HBx) plays a key role in the development of hepatocellular carcinoma (HCC) in HBV carriers. A drug that can bind to the promoter region of HBV may shut down the expression of HBx and subsequently prevent the development of HCC in the HBV carrier. We have constructed a seven amino acid residue peptide library on a TentaGel resin using a combinatorial one-bead one-sequence peptide synthesis method. The fluorescently labeled eicosanucleotide (5'-(6-FAM) CTTTTGGGCT TTGCTGCCCC-3') of the HBx promoter region was used as a monitor to screen for peptides that have high binding affinity to the HBx promoter. Two heptapeptides, KAPLFSI and SRVRMTW, were identified, and synthesized. The binding affinities of the peptides to the HBx promoter oligonucleotide were determined using Surface Plasmon Resonance (SPR). The peptide KAPLFSI had a greater binding affinity constant (k(a)) and equilibrium constant (K-D) than SRVRMTW. The k(a) and K-D values with the full X-promoter sequence were found to be 1.425 E+5 (1/Ms) and 1.186 E-8 (M), respectively. The peptide may open a new route for tumor suppression in HBV carriers.