Binding of topo I to PARP I - antibody immunocomplex

It is frequently quoted in the literature that the cellular role of PARP I is its participation in the recognition of single strand breaks of genomic DNA (l.c.1). Although there is little doubt that PARP I can be made to respond powerfully as an factor in the recognition of DNA damage, it seems unlikely that this auxilliary, or telelogically defined, role of this highly abundant nuclear protein exhausts its physiologic cellular function. We have reported that Topo I is greatly activated by its association with PARP I (J Mol Med 5: 533-540, 2000). Translation of this in vitro model experiments to physiologic conditions was accomplished by the demonstration of the quantitative binding of Topo I to a PARP I - antibody complex, as reported here. This experiment demonstrates for the first time that the colligative action of PARP I can regulate a highly significant cellular process, the control of readability of genomic DNA, i.e., gene expression, without the artificiality of induced DNA damage.