A Potent Conformation-Constrained Synthetic Peptide Mimic of a Homeodomain Selectively Regulates Target Genes in Cells

DNA, as a target for therapeutic intervention, remains largely unexplored. DLX-4, a homeodomain containing transcription factor, and its spliced isoforms play crucial roles in many aspects of cellular biochemistry and important roles in many diseases. A smaller peptide mimicking the homeodomain of the transcription factor DLX-4 was designed and synthesized by suitable conjoining of its modified DNA-binding elements. The peptide binds to DLX-4 target sites on the regulatory region of the globin gene cluster with native-like affinity and specificity in vitro. When conjugated to cell penetrating and nuclear localization sequences, it upregulated some of the genes repressed by DLX-4 or its isoforms, such as β- and γ-globin genes in erythropoietin-induced differentiating CD34⁺ human hematopoietic stem/progenitor cells with high specificity by competing with the respective binding sites. Engineered peptides mimicking DNA-binding domains of transcription factors offer the potential for creating synthetic molecules for directly targeting DNA sites with high specificity.