The integrity and proper expression of genomes are safeguarded by DNA and RNA surveillance pathways. While many RNA surveillance factors have additional functions in the nucleus, little is known... Show moreThe integrity and proper expression of genomes are safeguarded by DNA and RNA surveillance pathways. While many RNA surveillance factors have additional functions in the nucleus, little is known about the incidence and physiological impact of converging RNA and DNA signals. Here, using genetic screens and genome-wide analyses, we identified unforeseen SMG-1-dependent crosstalk between RNA surveillance and DNA repair in living animals. Defects in RNA processing, due to viable THO complex or PNN-1 mutations, induce a shift in DNA repair in dividing and non-dividing tissues. Loss of SMG-1, an ATM/ATR-like kinase central to RNA surveillance by nonsense-mediated decay (NMD), restores DNA repair and radio-resistance in THO-deficient animals. Mechanistically, we find SMG-1 and its downstream target SMG-2/UPF1, but not NMD per se, to suppress DNA repair by non-homologous end-joining in favour of single strand annealing. We postulate that moonlighting proteins create short-circuits in vivo, allowing aberrant RNA to redirect DNA repair. Show less
Kamp, J.A.; Lemmens, B.B.L.G.; Romeijn, R.J.; Changoer, S.C.; Schendel, R. van; Tijsterman, M. 2021
DNA double-strand breaks are a major threat to cellular survival and genetic integrity. In addition to high fidelity repair, three intrinsically mutagenic DNA break repair routes have been... Show moreDNA double-strand breaks are a major threat to cellular survival and genetic integrity. In addition to high fidelity repair, three intrinsically mutagenic DNA break repair routes have been described, i.e. single-strand annealing (SSA), polymerase theta-mediated end-joining (TMEJ) and residual ill-defined microhomology-mediated end-joining (MMEJ) activity. Here, we identify C. elegans Helicase Q (HELQ-1) as being essential for MMEJ as well as for SSA. We also find HELQ-1 to be crucial for the synthesis-dependent strand annealing (SDSA) mode of homologous recombination (HR). Loss of HELQ-1 leads to increased genome instability: patchwork insertions arise at deletion junctions due to abortive rounds of polymerase theta activity, and tandem duplications spontaneously accumulate in genomes of helq-1 mutant animals as a result of TMEJ of abrogated HR intermediates. Our work thus implicates HELQ activity for all DSB repair modes guided by complementary base pairs and provides mechanistic insight into mutational signatures common in HR-defective cancers.Microhomology-mediated end-joining (MMEJ) is a poorly defined mutagenic DNA break repair pathway. Here the authors show that the helicase HELQ is essential for polymerase theta-independent MMEJ, single-strand annealing and homologous recombination through synthesis dependent strand annealing in C. elegans. Show less
Kamp, J.A.; Lemmens, B.B.L.G.; Romeijn, R.J.; Changoer, S.C.; Schendel, R. van; Tijsterman, M. 2021
Homologous recombination is essential for repair of DNA interstrand cross-links and double-strand breaks. The Rad51C protein is one of the five Rad51 paralogs in vertebrates implicated in... Show moreHomologous recombination is essential for repair of DNA interstrand cross-links and double-strand breaks. The Rad51C protein is one of the five Rad51 paralogs in vertebrates implicated in homologous recombination. A previously described hamster cell mutant defective in Rad51C (CL-V4B) showed increased sensitivity to DNA damaging agents and displayed genomic instability. Here, we identified a splice donor mutation at position +5 of intron 5 of the Rad51C gene in this mutant, and generated mice harboring an analogous base pair alteration. Rad51C(splice) heterozygous animals are viable and do not display any phenotypic abnormalities, however homozygous Rad51C(splice) embryos die during early development (E8.5). Detailed analysis of two CL-V48 revertants, V4B-MR1 and V4B-MR2, that have reduced levels of full-length Rad51C transcript when compared to wild type hamster cells, showed increased sensitivity to mitomycin C (MMC) in clonogenic survival, suggesting haploinsufficiency of Rad51C. Similarly, mouse Rad51C(splice/neo) heterozygous ES cells also displayed increased MMC sensitivity. Moreover, in both hamster revertants, Rad51C haploinsufficiency gives rise to increased frequencies of spontaneous and MMC-induced chromosomal aberrations, impaired sister chromatid cohesion and reduced cloning efficiency. These results imply that adequate expression of Rad51C in mammalian cells is essential for maintaining genomic stability and sister chromatid cohesion to prevent malignant transformation. (C) 2010 Elsevier B.V. All rights reserved. Show less
Romeijn, R.J.; Gorski, M.M.; Schie, M.A. van; Noordermeer, J.N.; Mullenders, L.H.; Ferro, W.; Pastink, A. 2005
