Hypercapnia-inducible factor: a hypothesis

Abstract. Cells and tissues sense and respond to hypercapnia by global activation or down-regulation of hundreds of genes and switching on/off a number of signaling and metabolic pathways. We hypothesize for the first time that such complex rearrangements are hardly possible without subtle guidance by a specific master regulator which we suggest to name hypercapnia-inducible factor (HcIF). Whether there are structural and functional similarities between HcIF and HIF remain to be elucidated. However, there are reasons to believe that, as master genes, HcIF and HIF can cooperate or compete depending on the situation. Only further research will warrant existence of HcIF as a molecular master regulator of the response to hypercapnia. Key words: hypercapnia, hypoxia, gene expression, aging