UC San Diego

Polynucleotide kinase/phosphatase (PNKP) is an essential enzyme for DNA repair, and its dysfunction is related to many neurological diseases. However, how PNKP is regulated in nucleus is not fully understood yet. Our collaborator found that the metabolic enzyme 6-phosphofructokinase/fructose-2,6-biphosphatase 3 (PFKFB3) is a component of the PNKP-associated DNA repair complex. Since the major role of PFKFB3 is to produce Fru-2,6-P2, we hypothesized that Fru-2,6-P2 plays an important role in DNA repairing. I prepared and purified Fru-2,6-P2 in in vitro, and used both biochemical assay and binding experiments to show that Fru-2,6-P2 enhanced PNKP activity in vitro through direct binding. Moreover, I found that PNKP is phosphorylated by IκB Kinase 2 (IKK2) in vitro. Furthermore, I tested Fru-2,6-P2 level in spinocerebellar ataxia 3 (SCA3) patients and Huntington Disease patient samples (postmortem brains), and found that the Fru-2,6-P2 levels are lower in all SCA3 and most HD patient samples tested. Our results elucidate the significance of Fru-2,6-P2 and PFKFB3 in DNA repair and suggest that Fru-2,6-P2 plays an important role in many neurological diseases. Furthermore, in vitro studies on IKK2 phosphorylating PNKP indicates that IKK2 is a possible regulator of PNKP.