SAMHD1 Promotes DNA End Resection to Facilitate DNA Repair by Homologous Recombination

Daddacha, Waaqo; Koyen, Allyson; Bastien, Amanda J.; Head, PamelaSara E.; Dhere, Vishal R.; Nabeta, Geraldine; Connolly, Erin C.; Werner, Erica; Madden, Matthew Z.; Daly, Michele B.; Minten, Elizabeth; Whelan, Donna R.; Schlafstein, Ashley; Zhang, Hui; Anand, Roopesh; Doronio, Christine A.; Withers, Allison E.; Shepard, Caitlin; Sundaram, Ranjini K.; Deng, Xingming; Dynan, William S.; Wang, Ya; Bindra, Ranjit S.; Ćejka, Petr; Rothenberg, Eli; Doetsch, Paul W.; Kim, Baek; Yu, David S.

doi:10.1016/j.celrep.2017.08.008

Cited by 162 publications

(231 citation statements)

References 72 publications

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“…10 Besides the effects on dNTP pool composition, in normal human fibroblasts siRNA-silencing of SAMHD1 inhibits cell proliferation and disturbs the G1/S transition. 28 Considering the potential problems arising from the experimental suppression of SAMHD1 activity, here we chose to study the effects of an endogenous lack of SAMHD1 on cell proliferation and genomic stability in primary skin fibroblasts derived from four unrelated AGS patients carrying different SAMHD1 mutations. 15 In the case of transformed cells, the effects of SAMHD1 downregulation on cell cycle progression are controversial.…”

Section: Introductionmentioning

confidence: 99%

SAMHD1‐deficient fibroblasts from Aicardi‐Goutières Syndrome patients can escape senescence and accumulate mutations

et al. 2019

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In mammalian cells, the catabolic activity of the dNTP triphosphohydrolase SAMHD1 sets the balance and concentration of the four dNTPs. Deficiency of SAMHD1 leads to unequally increased pools and marked dNTP imbalance. Imbalanced dNTP pools increase mutation frequency in cancer cells, but it is not known if the SAMHD1induced dNTP imbalance favors accumulation of somatic mutations in nontransformed cells. Here, we have investigated how fibroblasts from Aicardi-Goutières Syndrome (AGS) patients with mutated SAMHD1 react to the constitutive pool imbalance characterized by a huge dGTP pool. We focused on the effects on dNTP pools, cell cycle progression, dynamics and fidelity of DNA replication, and efficiency of UV-induced DNA repair. AGS fibroblasts entered senescence prematurely or upregulated genes involved in G1/S transition and DNA replication. The normally growing AGS cells exhibited unchanged DNA replication dynamics and, when quiescent, faster rate of excision repair of UV-induced DNA damages. To investigate whether the lack of SAMHD1 affects DNA replication fidelity, we compared de novo mutations in AGS and WT cells by exome next-generation sequencing. Somatic variant analysis indicated a mutator phenotype suggesting that SAMHD1 is a caretaker gene whose deficiency is per se mutagenic, promoting genome instability in nontransformed cells.

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Section: Introductionmentioning

confidence: 99%

SAMHD1‐deficient fibroblasts from Aicardi‐Goutières Syndrome patients can escape senescence and accumulate mutations

et al. 2019

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“…SAMHD1 is also a homologous recombination (HR) factor and is involved in recruiting MRE11 to damaged DNA (45, 46). This role of SAMHD1 could also play an important role in its interaction with HPV16 as this virus recruits a host of HR factors to its replicating DNA and it is proposed that HPV16 using HR during viral replication in order to amplify its genome.…”

Section: Discussionmentioning

confidence: 99%

SAMHD1 regulates human papillomavirus 16 induced cell proliferation and viral replication during differentiation of oral keratinocytes

Morgan

James

Prabhakar

et al. 2019

Preprint

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4Human papillomaviruses induce a host of anogenital cancers, and also oropharyngeal cancer 5 (HPV+OPC); HPV16 is causative in around 90% of HPV+OPC. Using TERT immortalized 6 "normal" oral keratinocytes (NOKs) we have identified significant host gene reprogramming by 7 HPV16 (NOKs+HPV16), and demonstrated that NOKs+HPV16 support late stages of the viral life 8 cycle. Expression of the cellular dNTPase and homologous recombination factor SAMHD1 is 9 transcriptionally regulated by HPV16 in NOKs, and here we demonstrate that E6 and E7 regulate 10 expression of SAMHD1 at the transcriptional and post-transcriptional levels. CRISPR/Cas9 11 removal of SAMHD1 from NOKs and NOKs+HPV16 demonstrate that SAMHD1 controls cell 12 proliferation of NOKs only in the presence of HPV16; deletion of SAMHD1 promotes hyper-13 proliferation of NOKs+HPV16 cells in organotypic raft cultures but has no effect on NOKs. Viral 14 replication is also elevated in the absence of SAMHD1. This new system has allowed us to identify 15 a specific interaction between SAMHD1 and HPV16 that regulates host cell proliferation and viral 16 replication; such studies are problematic in non-immortalized primary oral keratinocytes due to 17 their limited lifespan. To confirm the relevance of our results we repeated the analysis with human 18 tonsil keratinocytes immortalized by HPV16 (HTK16) and observe the same hyper-proliferative 19 phenotype following CRISPR/Cas9 editing of SAMHD1. Identical results were obtained with three 20 independent CRISPR/Cas9 guide RNAs. The isogenic pairing of NOKs with NOKs+HPV16, 21 combined with HTK16, presents a unique system to identify host genes whose products 22 functionally interact with HPV16 to regulate host cellular growth in oral keratinocytes. 23 Importance 24Head and neck cancer is the sixth most common cancer worldwide. The incidence of HPV+OPC 25 has been rising steadily since the 1970s and has recently reached epidemic proportions, 26 according to the WHO. Upwards of 70% of the 600,000 new OPC cases per year are HPV 27 positive, with high-risk type 16 present in 90% of those incidences. A better understanding of the 28 viral life cycle will facilitate the development of novel therapeutics to combat this ongoing 29 3 epidemic, as well as other HPV positive cancers. Here we present a unique oral keratinocyte 30 model to identify host proteins that specifically interact with HPV16. Using this system, we report 31 that a cellular gene, SAMHD1, is regulated by HPV16 at the RNA and protein level in oral 32 keratinocytes. Elimination of SAMHD1 from these cells using CRISPR/Cas9 editing promotes 33 enhanced cellular proliferation by HPV16 in oral keratinocytes and elevated viral replication, but 34 not in keratinocytes that do not have HPV16. Our study demonstrates a specific intricate interplay 35 between HPV16 and SAMHD1 during the viral life cycle and establishes a unique model system 36 to assist exploring host factors critical for HPV pathogenesis. 37 38

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“…While the precise function of nucleic acid interaction in cells is yet to be determined, a recent report suggests that the ability of SAMHD1 to interact with DNA may play a crucial role in facilitating the repair of DNA. In this study, SAMHD1 was demonstrated to localize to sites of double stranded breaks and promote homologous recombination through its ability to form a complex with the endonuclease CtBP interacting protein (CtIP) (94). This description of a previously unidentified SAMHD1 role in DNA damage repair broadens the scope of the enzyme’s cellular functionality, and underscores the importance of further investigation of the dynamic cycle between nucleic acid bound inactive monomer-dimer and catalytically active tetramer.…”

Section: Samhd1 Activation Catalysis and Regulationmentioning

confidence: 99%

SAMHD1: Recurring roles in cell cycle, viral restriction, cancer, and innate immunity

Mauney

Hollis

2018

Autoimmunity

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SAMHD1 is a deoxynucleotide triphosphate (dNTP) hydrolase that plays an important role in the homeostatic balance of cellular dNTPs. Its emerging role as an effector of innate immunity is affirmed by mutations in the SAMHD1 gene that cause the severe autoimmune disease, Aicardi-Goutieres syndrome (AGS) and that are linked to cancer. Additionally, SAMHD1 functions as a restriction factor for retroviruses such as HIV. Here we review the current biochemical and biological properties of the enzyme including its structure, activity, and regulation by post-translational modifications in the context of its cellular function. We outline open questions regarding the biology of SAMHD1 whose answers will be important for understanding its function as a regulator of cell cycle progression, genomic integrity, and in autoimmunity.

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SAMHD1 Promotes DNA End Resection to Facilitate DNA Repair by Homologous Recombination

Cited by 162 publications

References 72 publications

SAMHD1‐deficient fibroblasts from Aicardi‐Goutières Syndrome patients can escape senescence and accumulate mutations

SAMHD1‐deficient fibroblasts from Aicardi‐Goutières Syndrome patients can escape senescence and accumulate mutations

SAMHD1 regulates human papillomavirus 16 induced cell proliferation and viral replication during differentiation of oral keratinocytes

SAMHD1: Recurring roles in cell cycle, viral restriction, cancer, and innate immunity

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