A High-Throughput\nScreen for Antiproliferative Peptides\nin Mammalian Cells Identifies Key Transcription Factor Families

Transcription factors (TFs) are a\npromising therapeutic\ntarget\nfor a multitude of diseases. TFs perform their cellular roles by participating\nin multiple specific protein–protein interactions. For example,\nhomo- or heterodimerization of some TFs controls DNA binding, while\ninteractions between TFs and components of basal transcriptional machinery\nor chromatin modifiers can also be critical. While, in theory, small\nmolecules could be used to disrupt specific protein–protein\ninterfaces required for TF function, in practice, it is difficult\nto identify small molecules with the necessary specificity and efficacy,\nlikely due to the extensive protein–protein interfaces that\noften underlie TF function. However, in contrast to small molecules,\npeptides have the potential to provide both the specificity and efficacy\nrequired to disrupt such interfaces. Here, we identified ∼15\npeptides that inhibit the proliferation of leukemia cells using a\nhigh-throughput pooled screen of a library of 80-mer protein regions\n(peptides) derived from human nuclear-localized proteins. The antiproliferative\npeptides were enriched for regions known to be involved in specific\nTF dimerization, including the basic leucine zipper (bZIP) domain\nfamily. One of these bZIP domains, JDP2;bZIP_1, from the TF JDP2,\nwas the top antiproliferative peptide, reducing the proliferation\nof K562 cells by 2-fold. JDP2;bZIP_1 inhibited AP-1 transcriptional\nactivity and phenocopied JDP2 overexpression, suggesting that the\npeptide affected proliferation through a native JDP2 mechanism. Unexpectedly,\ngiven the strong conservation of the bZIP domain, residues outside\nof the annotated dimerization domain were critical for the peptide’s\nantiproliferative potency. The peptide-mediated antiproliferative\neffect initiated erythrocyte differentiation in K562 cells and increased\nG0/G1 cells across multiple cell line models. We also found that many\nof the antiproliferative peptides identified in this study, including\nJDP2;bZIP_1, did not require a nuclear localization signal to function,\na potential benefit for delivering these peptides in therapeutic applications.