DNA damage affects the ability of the cell to transcribe ribosomal RNA by RNA pol I. The resumption of ribosome biogenesis following DNA damage is a key step in the cell recovering from acute DNA damage. We have utilized N2-4-ethynylbenzyl-2′-deoxyguanosine (EBndG) as a probe for DNA polymerase Κ (pol Κ) activity and have found that DNA that pol Κ is involved in the repair of ribosomal DNA following benzo[a]pyrene diol epoxide (BPDE) treatment. Mass spectra analysis of proteins bound to newly synthesize DNA containing EBndG showed enrichment of proteins involved in RNA binding, ribosome biogenesis, nucleolar proteins and transcriptional repressive complexes. Pol K was highly active in nucleolar DNA after BPDE damage, as detected by super-resolution confocal microscopy, following adduction to a fluorophore via copper-catalyzed cyclo-addition reactions. The incorporation of EBndG into the nucleolus activity is dependent on pol K expression, and partially dependent on the PCNA E3 ligase RAD18. The cellular levels of pol Κ were increased via stabilization of the protein while POLK transcript levels decreased. Using inhibitors and siRNA, the incorporation of EBndG into nucleolar DNA was dependent on PARP1 PARylation that recruits the polycomb complexes PRC1 and PRC2. These results suggest that BPDE treatment leads to the activation of PARP1 that activates PRC1/2 that in turn increase the activity of pol Κ in repair of ribosomal DNA.

DNA polymerase Κ is involved in ribsomal DNA repair after benzoypyrene diol epoxide damage

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