Domain structure of human HIF-1α, showing Plk3 phosphorylation sites. Human HIF-1α contains a basic helix-loop-helix domain (bHLH), a PAS domain, an oxygen-dependent degradation domain (ODDD), an N-terminal transactivation domain (N-TAD), and a C-terminal transactivation domain (C-TAD). The hydroxylation sites (P402, P564, and N803) are indicated. The Plk3 phosphorylation sites (S576, S657) are bolded. NES: nuclear exporting signal. NLS: nuclear localization signal.