Dysregulation of
the transcription factor MYC is involved in many
human cancers. The dimeric transcription factor complexes of MYC/MAX
and MAX/MAX activate or inhibit, respectively, gene transcription
upon binding to the same enhancer box DNA. Targeting these complexes
in cancer is a long-standing challenge. Inspired by the inhibitory
activity of the MAX/MAX dimer, we engineered covalently linked, synthetic
homo- and heterodimeric protein complexes to attenuate oncogenic MYC-driven
transcription. We prepared the covalent protein complexes (∼20
kDa, 167–231 residues) in a single shot via parallel automated
flow synthesis in hours. The stabilized covalent dimers display DNA
binding activity, are intrinsically cell-penetrant, and inhibit cancer
cell proliferation in different cell lines. RNA sequencing and gene
set enrichment analysis in A549 cancer cells confirmed that the synthetic
dimers interfere with MYC-driven transcription. Our results demonstrate
the potential of automated flow technology to rapidly deliver engineered
synthetic protein complex mimetics that can serve as a starting point
in developing inhibitors of MYC-driven cancer cell growth.