Directed Evolution of Peptide Inhibitors of Myc-Max Dimerization (PQ18)

描述（由申请人提供）：myc基因家族成员的表达失调是肿瘤进展和维持所必需的，并且与许多高度侵袭性和低分化的人类癌症有关。在一些肿瘤中，甚至短暂的Myc下调也会导致肿瘤消退。Myc作为相互作用的转录因子网络的一部分，每个转录因子都具有相关但不同的结构域，参与蛋白质相互作用和DNA结合。通过这个碱性螺旋环螺旋拉链（bHLHZip）结构域，Myc与Max形成高度特异的异源二聚体。Myc-Max异源二聚体结合了约15%的基因组位点，通常导致参与细胞生长、增殖、代谢、

DESCRIPTION (provided by applicant): Deregulation of the expression of myc gene family members is required for tumor progression and maintenance, and is associated with many highly aggressive and poorly differentiated human cancers. In some tumors even transient downregulation of Myc results in tumor regression. Myc functions as part of a network of interacting transcription factors each possessing related but distinct domains involved in protein interaction and DNA binding. Through this basic-helix-loop-helix-zipper (bHLHZip) domain, Myc forms highly specific heterodimers with Max. Myc-Max heterodimers bind ~15% of genomic loci, often resulting in transactivation of genes involved in cellular growth, proliferation, metabolism, apoptosis and differentiation. Conversely, Mxd transcription factors competitively bind to Max and repress Myc gene targets, acting as Myc antagonists. Here we propose to employ a newly developed technology to screen a library of ~600,000 variants of the Max zipper domain and identify peptides that will specifically inhibit Myc-Max dimerization, but not Mxd-Max. Because Mxd-Max heterodimers repress genes activated by Myc-Max we predict that disruption of Myc-Max alone will result in inhibition of Myc driven cell proliferation. Peptide inhibitors derived frm our screen will be tested in biochemical assays and tumor cells. Using computational modeling, directed evolution and biological validation, we will assess the molecular and functional mechanisms of inhibition to ensure protein specificity and therapeutic efficacy in reducing levels of activated Myc and attenuating tumor growth PUBLIC HEALTH RELEVANCE: The Myc protein is a major regulator of normal cell proliferation, but when the myc gene is disrupted its out-of-control expression drives tumor formation. In this study we propose to employ new genomic technology to generate a peptide inhibitor of Myc function that will arrest tumors dependent on Myc. We expect that this approach will serve as a model for developing inhibitors against other gene regulatory factors, in addition to Myc, that are critical for tumor progression.