Defective removal of ribonucleotides from DNA promotes systemic autoimmunity
Claudia Günther, … , Andrew P. Jackson, Min Ae Lee-Kirsch
Claudia Günther, … , Andrew P. Jackson, Min Ae Lee-Kirsch
Published December 15, 2014
Citation Information: J Clin Invest. 2015;125(1):413-424. https://doi.org/10.1172/JCI78001.
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Research Article

Defective removal of ribonucleotides from DNA promotes systemic autoimmunity

Abstract

Genome integrity is continuously challenged by the DNA damage that arises during normal cell metabolism. Biallelic mutations in the genes encoding the genome surveillance enzyme ribonuclease H2 (RNase H2) cause Aicardi-Goutières syndrome (AGS), a pediatric disorder that shares features with the autoimmune disease systemic lupus erythematosus (SLE). Here we determined that heterozygous parents of AGS patients exhibit an intermediate autoimmune phenotype and demonstrated a genetic association between rare RNASEH2 sequence variants and SLE. Evaluation of patient cells revealed that SLE- and AGS-associated mutations impair RNase H2 function and result in accumulation of ribonucleotides in genomic DNA. The ensuing chronic low level of DNA damage triggered a DNA damage response characterized by constitutive p53 phosphorylation and senescence. Patient fibroblasts exhibited constitutive upregulation of IFN-stimulated genes and an enhanced type I IFN response to the immunostimulatory nucleic acid polyinosinic:polycytidylic acid and UV light irradiation, linking RNase H2 deficiency to potentiation of innate immune signaling. Moreover, UV-induced cyclobutane pyrimidine dimer formation was markedly enhanced in ribonucleotide-containing DNA, providing a mechanism for photosensitivity in RNase H2–associated SLE. Collectively, our findings implicate RNase H2 in the pathogenesis of SLE and suggest a role of DNA damage–associated pathways in the initiation of autoimmunity.

Authors

Claudia Günther, Barbara Kind, Martin A.M. Reijns, Nicole Berndt, Manuel Martinez-Bueno, Christine Wolf, Victoria Tüngler, Osvaldo Chara, Young Ae Lee, Norbert Hübner, Louise Bicknell, Sophia Blum, Claudia Krug, Franziska Schmidt, Stefanie Kretschmer, Sarah Koss, Katy R. Astell, Georgia Ramantani, Anja Bauerfeind, David L. Morris, Deborah S. Cunninghame Graham, Doryen Bubeck, Andrea Leitch, Stuart H. Ralston, Elizabeth A. Blackburn, Manfred Gahr, Torsten Witte, Timothy J. Vyse, Inga Melchers, Elisabeth Mangold, Markus M. Nöthen, Martin Aringer, Annegret Kuhn, Kirsten Lüthke, Leonore Unger, Annette Bley, Alice Lorenzi, John D. Isaacs, Dimitra Alexopoulou, Karsten Conrad, Andreas Dahl, Axel Roers, Marta E. Alarcon-Riquelme, Andrew P. Jackson, Min Ae Lee-Kirsch

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Figure 3

Increased levels of misincorporated ribonucleotides in genomic DNA in cells from patients with AGS and SLE.

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Increased levels of misincorporated ribonucleotides in genomic DNA in ce...
(A) Representative images of comets formed by human fibroblasts after single-cell electrophoresis at alkaline and neutral pH without or with RNase H2 pretreatment. Scale bar: 50 μm. (B and C) Quantification of Olive tail moment (see Supplemental Methods) after alkaline comet assay, indicative of single-strand DNA breaks, in (B) fibroblasts from SLE patients (SLE1 and SLE2), AGS patients (AGS1 and AGS2), and WT controls (WT1 and WT2) and in (C) Rnaseh2b-deficient or WT MEFs. (D and E) Quantification of Olive tail moment in comet assays of human fibroblasts and MEFs (as in B and C, respectively) under neutral condition, without and with RNase H2 pretreatment, showed increased Olive tail moments for RNase H2–deficient cells, consistent with elevated levels of embedded ribonucleotides in their genomic DNA. (B–E) Mean and SEM of 30–70 cells from 3 independent experiments per cell line. **P < 0.01, ***P < 0.001 versus WT2 (B and D) or WT (C and E), t test.