Deletion of putative xenobiotic response elements (XREs) in hpol κ alters the replication stress response and overall genomic instability in glioblastoma cells

Abstract

Aberrant activation of human DNA polymerase kappa (hpol κ) via the kynurenine pathway-aryl hydrocarbon receptor (KP-AhR) pathway contributes to replication stress and genome instability in glioblastoma. Our previous studies relied solely on a small-molecule inhibitor of tryptophan 2-3-deoxygenase and an AhR antagonist. Xenobiotic response elements (XREs) are short DNA sequences present in gene promoter regions that act as binding sites for the ligand complexed AhR. To elucidate hpol κ regulation by KP-AhR, we generated POLK-ΔXRE cell lines using CRISPR/Cas9 editing. XRE ablation in glioblastoma cells led to decreased hpol κ expression. Disconnecting hpol κ transcriptional regulation from AhR signaling resulted in a diminished capacity for fork restart and a slight increase in degradation of forks stalled by hydroxyurea (HU). In spite of the reduced ability to resolve replication stress, the POLK-ΔXRE T98G cell lines had fewer micronuclei and ultra-fine bridges (UFBs), indicative of less chromosomal instability. These results further support the idea that hpol κ regulation by the AhR may influence the replication stress response and overall genomic instability in glioblastoma cells.