The present invention relates to oligooxopiperazines that mimic helix αB of the C-terminal transactivation domain of HIF-1α. Also disclosed are pharmaceutical compositions containing these oligooxopiperazines and methods of using these oligooxopiperazines (e.g., to reduce gene transcription, treat or prevent disorders mediated by interaction of HIF-1α with CREB-binding protein and/or p300, reduce or prevent angiogenesis in a tissue, induce apoptosis, and decrease cell survival and/or proliferation).