Nuclear phosphatidylinositol-5-phosphate regulates ING2 stability at discrete chromatin targets in response to DNA damage

ING2 (inhibitor of growth family member 2) is a component of a chromatin-regulatory complex that represses gene expression and is implicated in cellular processes that promote tumor suppression. However, few direct genomic targets of ING2 have been identified and the mechanism(s) by which ING2 selectively regulates genes remains unknown. Here we provide evidence that direct association of ING2 with the nuclear phosphoinositide phosphatidylinositol-5-phosphate (PtdIns(5) P) regulates a subset of ING2 targets in response to DNA damage. At these target genes, the binding event between ING2 and PtdIns(5) P is required for ING2 promoter occupancy and ING2-associated gene repression. Moreover, depletion of PtdIns(5) P attenuates ING2-mediated regulation of these targets in the presence of DNA damage. Taken together, these findings support a model in which PtdIns(5) P functions as a sub-nuclear trafficking factor that stabilizes ING2 at discrete genomic sites.