Functional interaction of poly(ADP-ribose) with the 20S proteasome in vitro

The nuclear enzyme poly(ADP-ribosyl) transferase (pADPRT) catalyzes the for mation of poly(ADP-ribose) from NAD(+). Several nuclear proteins and pADPRT itself are targets for the modification by poly(ADP-ribosyl)-ation. It is demonstrated here that poly(ADP-ribose) or pADPRT automodified with poly(AD P-ribose) interacts noncovalently with the 20S proteasome in vitro. The int eraction of pADPRT with the 20S proteasome requires the long ADP-ribose pol ymers formed by automodification of the pADPRT with poly(ADP-ribose), As a result pADPRT automodified with short ADP-ribose oligomers is unable to ass ociate with the 20S proteasome. The interaction with poly(ADP-ribose) cause s a specific stimulation of the peptidase activity of the 20S proteasome. M odified pADPRT does not serve as a substrate for the degradation by the 20S proteasome. No covalent modification of the 20S proteasome by ADP-ribosyla tion was observed. The results may point to a functional relationship betwe en pADPRT and the 20S proteasome in a pathway protecting the cell hom oxida tive damage. (C) 1999 Academic Press.