TRAIP promotes DNA damage response during genome replication and is mutated in primordial dwarfism.

DNA lesions encountered by replicative polymerases threaten genome stability and cell cycle progression. Here we report the identification of mutations in TRAIP, encoding an E3 RING ubiquitin ligase, in patients with microcephalic primordial dwarfism. We establish that TRAIP relocalizes to sites of DNA damage, where it is required for optimal phosphorylation of H2AX and RPA2 during S-phase in response to ultraviolet (UV) irradiation, as well as fork progression through UV-induced DNA lesions. TRAIP is necessary for efficient cell cycle progression and mutations in TRAIP therefore limit cellular proliferation, providing a potential mechanism for microcephaly and dwarfism phenotypes. Human genetics thus identifies TRAIP as a component of the DNA damage response to replication-blocking DNA lesions.This work was supported by funding from the Medical Research Council and the European Research Council (ERC, 281847) (A.P.J.), the Lister Institute for Preventative Medicine (A.P.J. and G.S.S.), Medical Research Scotland (L.S.B.), German Federal Ministry of Education and Research (BMBF, 01GM1404) and E-RARE network EuroMicro (B.W), Wellcome Trust (M. Hurles), CMMC (P.N.), Cancer Research UK (C17183/A13030) (G.S.S. and M.R.H), Swiss National Science Foundation (P2ZHP3_158709) (O.M.), AIRC (12710) and ERC/EU FP7 (CIG_303806) (S.S.), Cancer Research UK (C6/A11224) and ERC/EU FP7 (HEALTH-F2- 2010-259893) (A.N.B. and S.P.J.).This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/ng.345

Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism

To ensure efficient genome duplication, cells have evolved numerous factors that promote unperturbed DNA replication and protect, repair and restart damaged forks. Here we identify downstream neighbor of SON (DONSON) as a novel fork protection factor and report biallelic DONSON mutations in 29 individuals with microcephalic dwarfism. We demonstrate that DONSON is a replisome component that stabilizes forks during genome replication. Loss of DONSON leads to severe replication-associated DNA damage arising from nucleolytic cleavage of stalled replication forks. Furthermore, ATM- and Rad3-related (ATR)-dependent signaling in response to replication stress is impaired in DONSON-deficient cells, resulting in decreased checkpoint activity and the potentiation of chromosomal instability. Hypomorphic mutations in DONSON substantially reduce DONSON protein levels and impair fork stability in cells from patients, consistent with defective DNA replication underlying the disease phenotype. In summary, we have identified mutations in DONSON as a common cause of microcephalic dwarfism and established DONSON as a critical replication fork protein required for mammalian DNA replication and genome stability

Metastatic laryngeal carcinoma mimicking eruptive keratoacanthomas: report of keratoacanthoma-like cutaneous metastases in a radiation port

Metastatic skin lesions from a primary squamous cell carcinoma of the head and neck have only been reported in 1%–2% of these patients. Hence, skin metastases from laryngeal carcinoma are uncommon. Also, cutaneous metastases clinically presenting as a keratoacanthoma are rare. We describe cutaneous metastases in a radiation port clinically mimicking eruptive keratoacanthomas. Using the PubMed database, an extensive literature search was performed using the keywords cancer, carcinoma, keratoacanthoma, laryngeal, metastases, metastasis, metastatic, mimicking, port, radiation, radiotherapy, radiation, skin, visceral. We were able to summarize the features of patients with keratoacanthoma-like cutaneous metastases and discuss radiation port cutaneous metastases. Cutaneous metastases can be the initial manifestation of a previously undiagnosed malignancy or can present in a patient with an established diagnosis of cancer. Our patient not only developed skin metastases that mimicked eruptive keratoacanthomas, but to the best of our knowledge, is the first individual to develop radiation port cutaneous metastasis from a primary laryngeal carcinoma. The development of cutaneous metastases in an area of skin that has been treated with radiation therapy may result from the treatment altering and/or injuring the site, thereby making it more susceptible to another condition, such as metastatic skin tumors. In patients with an established diagnosis of visceral malignancy, the appearance of new keratoacanthoma-like lesions should prompt the clinician to consider a biopsy in order to establish or exclude the possibility of a cutaneous metastasis

Metastatic laryngeal carcinoma mimicking eruptive keratoacanthomas: report of keratoacanthoma-like cutaneous metastases in a radiation port

Metastatic skin lesions from a primary squamous cell carcinoma of the head and neck have only been reported in 1%–2% of these patients. Hence, skin metastases from laryngeal carcinoma are uncommon. Also, cutaneous metastases clinically presenting as a keratoacanthoma are rare. We describe cutaneous metastases in a radiation port clinically mimicking eruptive keratoacanthomas. Using the PubMed database, an extensive literature search was performed using the keywords cancer, carcinoma, keratoacanthoma, laryngeal, metastases, metastasis, metastatic, mimicking, port, radiation, radiotherapy, radiation, skin, visceral. We were able to summarize the features of patients with keratoacanthoma-like cutaneous metastases and discuss radiation port cutaneous metastases. Cutaneous metastases can be the initial manifestation of a previously undiagnosed malignancy or can present in a patient with an established diagnosis of cancer. Our patient not only developed skin metastases that mimicked eruptive keratoacanthomas, but to the best of our knowledge, is the first individual to develop radiation port cutaneous metastasis from a primary laryngeal carcinoma. The development of cutaneous metastases in an area of skin that has been treated with radiation therapy may result from the treatment altering and/or injuring the site, thereby making it more susceptible to another condition, such as metastatic skin tumors. In patients with an established diagnosis of visceral malignancy, the appearance of new keratoacanthoma-like lesions should prompt the clinician to consider a biopsy in order to establish or exclude the possibility of a cutaneous metastasis

CRISPR screens identify genomic ribonucleotides as a source of PARP-trapping lesions.

The observation that BRCA1- and BRCA2-deficient cells are sensitive to inhibitors of poly(ADP-ribose) polymerase (PARP) has spurred the development of cancer therapies that use these inhibitors to target deficiencies in homologous recombination. The cytotoxicity of PARP inhibitors depends on PARP trapping, the formation of non-covalent protein-DNA adducts composed of inhibited PARP1 bound to DNA lesions of unclear origins. To address the nature of such lesions and the cellular consequences of PARP trapping, we undertook three CRISPR (clustered regularly interspersed palindromic repeats) screens to identify genes and pathways that mediate cellular resistance to olaparib, a clinically approved PARP inhibitor. Here we present a high-confidence set of 73 genes, which when mutated cause increased sensitivity to PARP inhibitors. In addition to an expected enrichment for genes related to homologous recombination, we discovered that mutations in all three genes encoding ribonuclease H2 sensitized cells to PARP inhibition. We establish that the underlying cause of the PARP-inhibitor hypersensitivity of cells deficient in ribonuclease H2 is impaired ribonucleotide excision repair. Embedded ribonucleotides, which are abundant in the genome of cells deficient in ribonucleotide excision repair, are substrates for cleavage by topoisomerase 1, resulting in PARP-trapping lesions that impede DNA replication and endanger genome integrity. We conclude that genomic ribonucleotides are a hitherto unappreciated source of PARP-trapping DNA lesions, and that the frequent deletion of RNASEH2B in metastatic prostate cancer and chronic lymphocytic leukaemia could provide an opportunity to exploit these findings therapeutically