The apoptotic endonuclease DFF40/CAD is inhibited by RNA, heparin and other polyanions.
DFF40/CAD, the major apoptotic nuclease, is specific for double-stranded DNA. However, RNA and single-stranded DNA, though not substrates for the enzyme, compete with double-stranded DNA and inhibit its cleavage by the nuclease. In addition, other anionic polymers, like poly-glutamic acid and heparin also inhibit DFF40/CAD, the latter one being highly effective at nanomolar concentrations. The inhibitory poly-anions bind to the nuclease and impair its ability to bind double-stranded DNA. We propose that such poly-anions bind to the positively charged surface formed by alpha4 helices of the DFF40/CAD homodimer. This surface has been proposed recently to bind to either the major groove of DNA or poly (ADP-ribose), another inhibitor of the nuclease.
Widlak
Piotr
P
Department of Experimental and Clinical Radiobiology, Maria Sklodowska-Curie Cancer Center and Institute of Oncology, 44-100 Gliwice, Poland. widlak@io.gliwice.pl
Garrard
William T
WT
D017209:Apoptosis / Q000187:drug effects*; D004247:DNA / Q000378:metabolism; D003851:Deoxyribonucleases / Q000037:antagonists & inhibitors*; D018922:HL-60 Cells; D006493:Heparin / Q000494:pharmacology*; D006801:Humans; D000075223:Poly-ADP-Ribose Binding Proteins; D011099:Polyglutamic Acid / Q000494:pharmacology*; D012313:RNA / Q000494:pharmacology*
D000075223:Poly-ADP-Ribose Binding Proteins; D011099:Polyglutamic Acid; D012313:RNA; D006493:Heparin; D004247:DNA; C113696:DFFB protein, human; D003851:Deoxyribonucleases