Under conditions of severe DNA damage the nuclear enzyme poly(ADP-ribose) p
olymerase 1 (PARP-1) is activated, catalyzing the modification of proteins
by forming and attaching to them poly(ADP-ribose) chains. A specific physic
al interaction between PARP-1 and transcription factor Yin Yang 1 (YY1) in
vitro was shown previously, which had important consequences for the activi
ties of both proteins. It is demonstrated here that YY1 and PARP-1 form com
plexes in vivo. YY1 was transiently poly(ADP-ribosyl)ated immediately after
genotoxic treatment of HeLa cells. The narrow time frame of the modificati
on coincides with that known for the activation of PARP-1 under these condi
tions. This immediate modification correlated with a decreased affinity of
YY1 to its cognate DNA binding sites. (C) 2001 Academic Press.