Topoisomerase III super(2) associates with Ku70 and PARP-1 during double strand break repair of DNA in neurons

In the present study, the activity of Topoisomerase II beta (TopoII beta ) is evaluated during peroxide induced double stranded DNA breaks (DSBs) repair in primary neurons. The results showed that the TopoII beta levels were enhanced during recovery from peroxide mediated damage (PED) along with Ku70, PARP-1, pol beta, and WRN helicase. Furthermore, siRNA mediated knock-down of TopoII beta in primary neurons conferred enhanced susceptibility to PED in neurons. DSBs in neurons are repaired through two pathways, one promoted by Ku70, while the other is by PARP-1 dependent manner. Participation of TopoII beta in both pathways was assessed by analysis of the interaction of TopoII beta with Ku70 and PARP-1 using co-immunoprecipitation experiments in extracts of neurons under peroxide treatment and recovery. The results of these studies showed a strong interaction of TopoII beta with Ku70 as well as PARP-1 suggesting that TopoII beta is associated both in Ku70 and PARP-dependent pathways in DSBs repair in primary neurons. The study has thus established that TopoII beta is an essential component in DSBs repair in primary neurons in both Ku70 and PARP-1 dependent pathways. We suppose that the interaction of TopoII beta may provide stabilization of the repair complex, which may assist in maintenance of tensional integrity in genomic DNA.