Novel mechanisms of DNA damage and replication stress signaling: Functional roles of the WDR82/PNUTS-PP1 phosphatase complex

Abstract

DNA damaging agents, such as ionizing radiation and many chemotherapeutic drugs, are used in cancer treatment to kill cancer cells. However, networks of signaling cascades induced by DNA damage counteract this by leading to repair of damaged DNA. The ATR kinase is a key component of these signaling networks. We have explored mechanisms of how ATR can be activated. We found that ATR can be activated by phosphorylated RNA polymerase II (RNAPII), the enzyme that reads the DNA code to make messenger RNA in the process of transcription. The RNAPII phosphatase PNUTS-PP1 and two other RNAPII binding proteins, WDR82 and CDC73, were involved in regulating ATR activity. In addition, we found that proper dephosphorylation of RNAPII is important for normal DNA replication since hyperphosphorylated RNAPII is retained on DNA and can cause collisions between RNAPII and the replication machinery. We further explored whether this may sensitize cancer cells to a drug that perturbs DNA replication. Indeed, this drug induced more DNA damage and cell death in cancer cells with reduced levels of WDR82. Altogether our results provide new basic knowledge about DNA damage signaling cascades. This knowledge may potentially be exploited to improve future cancer treatment.