Fig. 1

Stability of HIF-1 in normoxia, hypoxia, and pseudohypoxia under varying oxygen levels. (i) Normoxia. HIF-1α is hydroxylated by PHD2, which leads to its ubiquitination and subsequent degradation by the proteasome, resulting in being unable to initiate transcription and regulate downstream genes. (ii) Hypoxia. HIF-1α cannot be hydroxylated by PHD2 nor be degraded by the proteasome. Consequently, HIF-1 can effectively perform its functions by binding to HIF1β in the transcription of downstream genes. (iii) Pseudohypoxia. HIF-1 remains stable and continues to regulate the transcription of downstream genes, even in the presence of oxygen