HIF1A and Sepsis: However, when both HIF proteins are absent in hepatocytes, we were no longer able to detect a significant increase in the HRE-luciferase activity in sepsis (Figures 4C, F), suggesting that both HIF1α and HIF2α are responsible for the HIF activity in sepsis and that perhaps both proteins can functionally compensate for the loss of the other in hepatocytes.