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.