Beyond a platform protein for the degradosome assembly: The Apoptosis Inducing Factor as efficient nuclease involved in chromatinolysis
The Apoptosis-Inducing Factor (AIF) is a moonlighting flavoenzyme involved in the assembly of mitochondrial respiratory complexes in healthy cells, but also able to trigger DNA cleavage and parthanatos. Upon apoptotic-stimuli, AIF redistributes from the mitochondria to the nucleus, where upon association with other proteins such as endonuclease CypA and histone H2AX, it is proposed to organize a DNA-degradosome complex. In this work, we provide evidence for the molecular assembly of this complex as well as for the cooperative effects among its protein components to degrade genomic DNA into large fragments. We have also uncovered that AIF has nuclease activity that is stimulated in the presence of either Mg2+ or Ca2+. Such activity allows AIF by itself and in cooperation with CypA to efficiently degrade genomic DNA. Finally, we have identified TopIB and DEK motifs in AIF as responsible for its nuclease activity. These new findings point, for the first time, to AIF as a nuclease able to digest nuclear dsDNA in dying cells, improving our understanding of its role in promoting apoptosis and opening paths for the development of new therapeutic strategies.