Abstract
DNA polymerase kappa (Polκ) has multiple cellular roles such as translesion DNA synthesis, replication of repetitive sequences and nucleotide excision repair. However, the mechanisms regulating Polκ’s cellular activities are unknown. Since all polymerases insert the canonical deoxynucleotide triphosphates, it is difficult to determine which polymerase is active at a particular genomic site. To counter this difficulty, we utilized the selective Polκ substrate, N2-(4-ethynylbenyl)-2’-deoxyguanosine (EBndG), as bait to capture proteins associated with Polκ synthesized DNA. Here we show that, Polκ is active in the nucleolus and Polκ synthesized DNA are enriched with nucleolar proteins. Exposure of cells to benzo[a]pyrene diol epoxide (BPDE) induced hallmarks of nucleolar stress, increased Polκ stability and nucleolar activity. Other agents that induce nucleolar stress such as mitomycin C, cisplatin and actinomycin D also increased Polκ’s nucleolar activity. The Polκ activity was cell-cycle independent and dependent on PCNA ubiquitination. In addition, we identified that the expression and activity of Polκ is regulated by the polycomb complex protein Ring Finger Protein 2 (RNF2) and by poly(ADP)-ribose polymerase 1 (PARP1) catalyzed PARylation. This study provides insight into the novel role of Polκ in ribosomal RNA synthesis, in maintaining ribosomal DNA integrity after DNA damage thus protecting the cells from nucleolar stress.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Revised manuscript
