The present invention relates to peptides having one or more stable, internally constrained α-helices, and that include a sequence that mimics at least a portion of the C-terminal transactivation domain of HIF-lα. Also disclosed are pharmaceutical compositions containing these peptides and methods of using these peptides, for example to reduce gene transcription, treat or prevent disorders mediated by interaction of HIF-lα with CREB-binding protein and/or p300, reduce or prevent angiogenesis in a tissue, induce apoptosis, decrease cell survival and/or proliferation, and identify potential ligands of CREB-binding protein and/or p300.
