Figure 1: Biological functions of APE1. APE1 is a multifunctional enzyme with distinct functions: a) repair function displayed through C-terminal segment with AP endonuclease activity; b) redox function displayed through disordered N-terminus as a reductive activator of various TFs (eg., HIF- 1α, p53, AP-1, & NF-κB); and c) recently discovered activities such as RNA metabolism, riboendonuclease activity and protein-protein interaction displayed through both C- and N-terminus of this protein.