Sci. Adv. 2021
Loss of PrimPol S538 phosphorylation affects genomic stability after UV-C damage and is dependent on RPA interaction
(A) Damage sensitivity was measured by colony survival after increasing doses of UV-C (left) or cisplatin (right). (B) Quantification of cell cycle recovery after damage was measured by flow cytometry, using EdU and PI labeling 24 hours after treatment with 5 J/m2 UV-C, images shown in fig. S4B. (C) Cells with one or more micronuclei were counted 48 hours after 5 J/m2 UV-C treatment. (D) CldU/IdU ratios show replication changes after a pulse of 20 J/m2 UV-C was given between labels. (E) Undamaged replication fork speeds were measured in the different cell lines at least 16 hours after PrimPol expression by labeling cells consecutively with CldU and IdU. (F) UV sensitivity was analyzed by colony survival in ΔPP-1 cells expressing RAB mutated forms of PrimPol also carrying the 538 mutations. (G) The effect of loss of PrimPol’s RPA interaction in micronuclei formation was compared in cells expressing PrimPol mutants additionally carrying the RAB mutations, 48 hours after exposure to 5 J/m2 UV-C.
Aidan J. Doherty Research Group
Significance
Replication stress and DNA damage stall replication forks and impede genome synthesis. During S phase, damage tolerance pathways allow lesion bypass to ensure efficient genome duplication. One such pathway is repriming, mediated by Primase-Polymerase (PrimPol) in human cells. However, the mechanisms by which PrimPol is regulated are poorly understood. Here, A. Doherty et al. demonstrate that PrimPol is phosphorylated by Polo-like kinase 1 (PLK1) at a conserved residue between PrimPol’s RPA binding motifs. This phosphorylation is differentially modified throughout the cell cycle, which prevents aberrant recruitment of PrimPol to chromatin. Phosphorylation can also be delayed and reversed in response to replication stress. The absence of PLK1-dependent regulation of PrimPol induces phenotypes including chromosome breaks, micronuclei, and decreased survival after treatment with camptothecin, olaparib, and UV-C. Together, these findings establish that deregulated repriming leads to genomic instability, highlighting the importance of regulating this damage tolerance pathway following fork stalling and throughout the cell cycle.
Bailey, L. J.; Teague, R.; Kolesar, P.; Bainbridge, L. J.; Lindsay, H. D. & Doherty, A. J.: PLK1 regulates the PrimPol damage tolerance pathway during the cell cycle, Sci. Adv. 2021, 7, eabh1004, https://doi.org/10.1126/sciadv.abh1004