title: Contrasting nuclear dynamics of the caspase-activated DNase (CAD) in dividing and apoptotic cells.
abstract: Although compelling evidence supports the central role of caspase-activated DNase (CAD) in oligonucleosomal DNA fragmentation in apoptotic nuclei, the regulation of CAD activity remains elusive in vivo. We used fluorescence photobleaching and biochemical techniques to investigate the molecular dynamics of CAD. The CAD-GFP fusion protein complexed with its inhibitor (ICAD) was as mobile as nuclear GFP in the nucleosol of dividing cells. Upon induction of caspase-3-dependent apoptosis, activated CAD underwent progressive immobilization, paralleled by its attenuated extractability from the nucleus. CAD immobilization was mediated by its NH2 terminus independently of its DNA-binding activity and correlated with its association to the interchromosomal space. Preventing the nuclear attachment of CAD provoked its extracellular release from apoptotic cells. We propose a novel paradigm for the regulation of CAD in the nucleus, involving unrestricted accessibility of chromosomal DNA at the initial phase of apoptosis, followed by its nuclear immobilization that may prevent the release of the active nuclease into the extracellular environment.
authors.affiliation: Hospital for Sick Children Research Institute and Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada.
authors.forename: Delphine
authors.initials: D
authors.lastname: Lechardeur
authors.forename: Ming
authors.initials: M
authors.lastname: Xu
authors.forename: Gergely L
authors.initials: GL
authors.lastname: Lukacs
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D019556:COS Cells; D053148:Caspase 3; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000235:genetics*; D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics; D006224:Cricetinae; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D003851:Deoxyribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D004247:DNA; D003851:Deoxyribonucleases; C109663:caspase-activated deoxyribonuclease; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases