title: Apoptotic DNA fragmentation may be a cooperative activity between caspase-activated deoxyribonuclease and the poly(ADP-ribose) polymerase-regulated DNAS1L3, an endoplasmic reticulum-localized endonuclease that translocates to the nucleus during apoptosis.
abstract: Caspase-activated DNase (CAD) is the most favorable candidate for chromatin degradation during apoptosis. Ca(2+)-dependent endonucleases are equally important in internucleosomal DNA fragmentation (INDF), including the PARP-1-regulated DNAS1L3. Despite the elaborate work on these endonucleases, the question of whether these enzymes cooperate during INDF was not addressed. Here, we show a lack of correlation between INDF and CAD expression levels and inactivation by cleavage of its inhibitor (ICAD) during apoptosis. The cells that failed to induce INDF accumulated large amounts of 50-kb breaks, which is suggestive of incomplete chromatin processing. Similarly, INDF was blocked by Ca(2+) chelation without a block in ICAD cleavage or caspase-3 activation, which is consistent with the involvement of CAD in 50-kb DNA fragmentation and its Ca(2+) independence. However, DNAS1L3 expression in INDF-deficient cells promoted INDF during apoptosis and was blocked by Ca(2+) chelation. Interestingly, expression of DNAS1L3 in ICAD-deficient cells failed to promote tumor necrosis factor α-induced INDF but required the coexpression of ICAD. These results suggest a cooperative activity between CAD and DNAS1L3 to accomplish INDF. In HT-29 cells, endogenous DNAS1L3 localized to the endoplasmic reticulum (ER) and translocated to the nucleus upon apoptosis induction but prior to INDF manifestation, making it the first reported Ca(2+)-dependent endonuclease to migrate from the ER to the nucleus. The nuclear accumulation of DNAS1L3, but not its exit out of the ER, required the activity of cysteine and serine proteases. Interestingly, the endonuclease accumulated in the cytosol upon inhibition of serine, but not cysteine, proteases. These results exemplify the complexity of chromatin degradation during apoptosis.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA.
authors.forename: Youssef
authors.initials: Y
authors.lastname: Errami
authors.forename: Amarjit S
authors.initials: AS
authors.lastname: Naura
authors.forename: Hogyoung
authors.initials: H
authors.lastname: Kim
authors.forename: Jihang
authors.initials: J
authors.lastname: Ju
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Ali H
authors.initials: AH
authors.lastname: El-Bahrawy
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Ghonim
authors.forename: Ramadan A
authors.initials: RA
authors.lastname: Hemeida
authors.forename: Moselhy S
authors.initials: MS
authors.lastname: Mansy
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
authors.forename: Ming
authors.initials: M
authors.lastname: Xu
authors.forename: Mark E
authors.initials: ME
authors.lastname: Smulson
authors.forename: Hassan
authors.initials: H
authors.lastname: Brim
authors.forename: A Hamid
authors.initials: AH
authors.lastname: Boulares
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D020029:Base Pairing; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology*; D057056:Cysteine Proteases / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D003851:Deoxyribonucleases / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology*; D005047:Etoposide; D017405:Herpes Simplex Virus Protein Vmw65 / Q000378:metabolism; D006801:Humans; D051379:Mice; D009707:Nucleosomes / Q000187:drug effects / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D057057:Serine Proteases / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D017405:Herpes Simplex Virus Protein Vmw65; D009707:Nucleosomes; D011480:Protease Inhibitors; C109664:caspase-activated DNase inhibitor; D005047:Etoposide; D011065:Poly(ADP-ribose) Polymerases; C485421:DNASE1L3 protein, human; D003851:Deoxyribonucleases; D004706:Endodeoxyribonucleases; C109663:caspase-activated deoxyribonuclease; D057056:Cysteine Proteases; D057057:Serine Proteases; D002118:Calcium