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Ferdinand Roesch, Molly OhAinle, Michael Emerman
The InterFeron Induced TransMembrane (IFITM) proteins are interferon stimulated genes that restrict many viruses, including HIV-1. SAMHD1 is another restriction factor blocking replication of HIV-1 and other viruses. Some lentiviruses evolved Vpx/Vpr proteins to degrade SAMHD1. However, this viral antagonism can be perturbed by host mechanisms: a recent study showed that in interferon (IFN) treated THP1 cells, Vpx is unable to degrade SAMHD1. In the present work, we designed an Interferon Stimulated Genes (ISGs)-targeted CRISPR knockout screen in order to identify ISGs regulating this phenotype...
March 20, 2018: Retrovirology
Allison A Lindgren, Adam R Filipowicz, Julian B Hattler, Soon Ok Kim, Hye Kyung Chung, Marcelo J Kuroda, Edward M Johnson, Woong-Ki Kim
OBJECTIVE: HIV-1 infection of the brain and related cognitive impairment remain prevalent in HIV-1-infected subjects despite combination antiretroviral therapy. Sterile alpha motif and histidine-aspartate domain-containing protein 1 (SAMHD1) is a newly identified host restriction factor that blocks the replication of HIV-1 and other retroviruses in myeloid cells. Cell-cycle-regulated phosphorylation at residue Thr592 and viral protein X (Vpx)-mediated degradation of SAMHD1 have been shown to bypass SAMHD1 restriction in vitro...
March 15, 2018: AIDS
Paula Jáuregui, Nathaniel R Landau
Monocyte-derived macrophages (MDMs) are an important target for HIV-1 despite SAMHD1, a myeloid restriction factor for which HIV-1 lacks a counteracting accessory protein. The antiviral activity of SAMHD1 is modulated by phosphorylation of T592 by cyclin-dependent kinases (CDK). We show that treatment of MDMs with neocarzinostatin, a compound that introduces double strand breaks (DBS) in genomic DNA, results in the decrease of phosphorylated SAMHD1, activating its antiviral activity and blocking HIV-1 infection...
March 7, 2018: Scientific Reports
Dibya Ghimire, Madhu Rai, Ritu Gaur
Human immunodeficiency virus-1 (HIV-1) is known to interact with multiple host cellular proteins during its replication in the target cell. While many of these host cellular proteins facilitate viral replication, a number of them are reported to inhibit HIV-1 replication at various stages of its life cycle. These host cellular proteins, which are known as restriction factors, constitute an integral part of the host's first line of defence against the viral pathogen. Since the discovery of apolipoprotein B mRNA-editing enzyme 3G (APOBEC3G) as an HIV-1 restriction factor, several human proteins have been identified that exhibit anti-HIV-1 restriction...
February 19, 2018: Journal of General Virology
Olga Buzovetsky, Chenxiang Tang, Kirsten M Knecht, Jenna M Antonucci, Li Wu, Xiaoyun Ji, Yong Xiong
Human SAMHD1 (hSAMHD1) is a retroviral restriction factor that blocks HIV-1 infection by depleting the cellular nucleotides required for viral reverse transcription. SAMHD1 is allosterically activated by nucleotides that induce assembly of the active tetramer. Although the catalytic core of hSAMHD1 has been studied extensively, previous structures have not captured the regulatory SAM domain. Here we report the crystal structure of full-length SAMHD1 by capturing mouse SAMHD1 (mSAMHD1) structures in three different nucleotide bound states...
January 29, 2018: Nature Communications
Patricia Johansson, Ludger Klein-Hitpass, Axel Choidas, Peter Habenberger, Bijan Mahboubi, Baek Kim, Anke Bergmann, René Scholtysik, Martina Brauser, Anna Lollies, Reiner Siebert, Thorsten Zenz, Ulrich Dührsen, Ralf Küppers, Jan Dürig
T-cell prolymphocytic leukemia (T-PLL) is an aggressive malignancy with a median survival of the patients of less than two years. Besides characteristic chromosomal translocations, frequent mutations affect the ATM gene, JAK/STAT pathway members, and epigenetic regulators. We here performed a targeted mutation analysis for 40 genes selected from a RNA sequencing of 10 T-PLL in a collection of 28 T-PLL, and an exome analysis of five further cases. Nonsynonymous mutations were identified in 30 of the 40 genes, 18 being recurrently mutated...
January 19, 2018: Blood Cancer Journal
Kavita Raniga, Chen Liang
Viruses exploit the host and induce drastic metabolic changes to ensure an optimal environment for replication and the production of viral progenies. In response, the host has developed diverse countermeasures to sense and limit these alterations to combat viral infection. One such host mechanism is through interferon signaling. Interferons are cytokines that enhances the transcription of hundreds of interferon-stimulated genes (ISGs) whose products are key players in the innate immune response to viral infection...
January 13, 2018: Viruses
Ryoko Koga, Minami Yamamoto, Halil Ibrahim Ciftci, Masami Otsuka, Mikako Fujita
Human immunodeficiency virus type 2 has two structurally similar proteins, Vpx and Vpr. Vpx degrades the host anti-viral protein SAMHD1 and is expressed at high levels, while Vpr is responsible for cell cycle arrest and is expressed at much lower levels. We constructed a Vpr mutant with a high level of expression by replacing the amino acids HHCR/HHCH with a putative H2C2-type zinc-binding site that is carried by Vpx. Our finding suggests that during the evolution of Vpr and Vpx, zinc-binding likely became a mechanism for regulating their expression levels...
January 2018: FEBS Open Bio
Corine St Gelais, Sun Hee Kim, Victoria V Maksimova, Olga Buzovetsky, Kirsten Knecht, Caitlin Shepard, Baek Kim, Yong Xiong, Li Wu
Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) regulates intracellular deoxynucleoside triphosphate (dNTP) levels and functions as a retroviral restriction factor through its dNTP triphosphohydrolase (dNTPase) activity. Human SAMHD1 interacts with cell cycle regulatory proteins cyclin A2, cyclin-dependent kinase 1 (CDK1), and CDK2. This interaction mediates phosphorylation of SAMHD1 at threonine 592 (T592), which negatively regulates HIV-1 restriction. We previously reported that the interaction is mediated, at least in part, through a cyclin-binding motif (RXL, aa...
January 10, 2018: Journal of Virology
Changhoon Oh, Jeongmin Ryoo, Kiwon Park, Baek Kim, Michele B Daly, DongYeon Cho, Kwangseog Ahn
The autoimmune disorder Aicardi-Goutières syndrome (AGS) is characterized by a constitutive type I interferon response. SAMHD1 possesses both dNTPase and RNase activities and mutations in SAMHD1 cause AGS; however, how SAMHD1-deficiency causes the type I interferon response in patients with AGS remains unknown. Here, we show that endogenous RNA substrates accumulated in the absence of SAMHD1 act as a major immunogenic source for the type I interferon response. Reconstitution of SAMHD1-negative human cells with wild-type but not RNase-defective SAMHD1 abolishes spontaneous type I interferon induction...
January 8, 2018: Scientific Reports
Allen Ka Loon Cheung, Yiru Huang, Hau Yee Kwok, Min Chen, Zhiwei Chen
Individuals who have been preinfected by human cytomegalovirus (HCMV) are more prone to AIDS disease progression after subsequent HIV-1 infection but the underlying mechanism remains elusive. HCMV is a ubiquitous DNA virus that commonly establishes lifelong latent infection in CD34+ progenitor cells, where latency-specific HCMV genes may modulate host restriction to HIV-1 infection. To test this hypothesis, we studied progenitor cells that are known to resist replicative HIV-1 infection because of the intrinsic expression of host restriction factors...
January 24, 2017: Blood Advances
Yu-Ting Wang, Bo Yuan, Hua-Dong Chen, Lin Xu, Yu-Nan Tian, Ao Zhang, Jin-Xue He, Ze-Hong Miao
With increasing uses of PARP inhibitors (PARPis) for cancer therapy, understanding their resistance is becoming urgent. However, acquired PARPi resistance in the PTEN-deficient background is poorly understood. We generated 3 PARPi-resistant PTEN-deficient glioblastoma U251 variants separately with olaparib (U251/OP), talazoparib (U251/TP) and simmiparib (U251/SP). These variants displayed consistent resistance (2.46~71.78-fold) to all 5 PARPis including niraparib and rucaparib and showed higher degrees of resistance to the PARPis to which the parental cells were more sensitive...
December 22, 2017: Cancer Science
Peyman Asadian, Gillian Finnie, Dorothee Bienzle
SAMHD1 restricts lentiviruses by limiting availability of deoxynucleoside triphosphates for reverse transcription. HIV-2 and SIV have virion-associated proteins to counteract SAMHD1. Cats have an ortholog to human SAMHD1 and the FIV is restricted by human SAMHD1, but expression of feline SAMHD1 is unknown. Using a whole-body tissue microarray consisting of 24 tissues for immunohistochemistry, SAMHD1 expression was identified in a wide range of cat tissues. SAMHD1 was most strongly expressed in skin and mucosal epithelium, and in hemolymphatic and spermatogenic tissues...
January 2018: Veterinary Immunology and Immunopathology
Fuad Al Mutairi, Majid Alfadhel, Marwan Nashabat, Ayman W El-Hattab, Tawfeg Ben-Omran, Jozef Hertecant, Wafaa Eyaid, Rehab Ali, Ali Alasmari, Majdi Kara, Waleed Al-Twaijri, Rana Filimban, Abduljabbar Alshenqiti, Mohammed Al-Owain, Eissa Faqeih, Fowzan S Alkuraya
BACKGROUND: Aicardi-Goutières syndrome is a rare genetic neurological disorder with variable clinical manifestations. Molecular detection of specific mutations is required to confirm the diagnosis. The aim of this study was to review the clinical and molecular diagnostic findings in 24 individuals with Aicardi-Goutières syndrome who presented during childhood in an Arab population. MATERIALS AND METHODS: We reviewed the records of 24 patients from six tertiary hospitals in different Arab countries...
January 2018: Pediatric Neurology
Jenna M Antonucci, Corine St Gelais, Li Wu
The innate immune response constitutes the first cellular line of defense against initial HIV-1 infection. Immune cells sense invading virus and trigger signaling cascades that induce antiviral defenses to control or eliminate infection. Professional antigen-presenting cells located in mucosal tissues, including dendritic cells and macrophages, are critical for recognizing HIV-1 at the site of initial exposure. These cells are less permissive to HIV-1 infection compared to activated CD4+ T-cells, which is mainly due to host restriction factors that serve an immediate role in controlling the establishment or spread of viral infection...
2017: Frontiers in Immunology
Patricia Costa-Reis, Kathleen E Sullivan
Monogenic lupus is rare, but its study has contributed immensely to a better understanding of the pathogenesis of systemic lupus erythematosus. The first forms identified were inherited complement deficiencies, which predisposed to lupus due to impaired tolerance, and aberrant clearance of apoptotic bodies and immune complexes. In recent years, several new monogenic disorders with a lupus-like phenotype have been described. These include forms that affect nucleic acid repair, degradation and sensing (TREX1, DNASE1L3), the type I interferon (IFN) pathway (SAMHD1, RNASEH2ABC, ADAR1, IFIH1, ISG15, ACP5, TMEM173) and B cell development checkpoints (PRKCD; RAG2)...
December 2017: Current Opinion in Immunology
Eun Ji Lee, Ji Hae Seo, Ji-Hyeon Park, Tam Thuy Lu Vo, Sunho An, Sung-Jin Bae, Hoang Le, Hye Shin Lee, Hee-Jun Wee, Danbi Lee, Young-Hwa Chung, Jeong A Kim, Myoung-Kuk Jang, Soo Hyung Ryu, Ensil Yu, Se Hwan Jang, Zee Yong Park, Kyu-Won Kim
SAM domain and HD domain containing protein 1 (SAMHD1) is a deoxynucleotide triphosphohydrolase (dNTPase) that inhibits retroviruses by depleting intracellular deoxynucleotide triphosphates (dNTPs) in non-cycling myeloid cells. Although SAMHD1 is expressed ubiquitously throughout the human body, the molecular mechanisms regulating its enzymatic activity and function in non-immune cells are relatively unexplored. Here, we demonstrate that the dNTPase activity of SAMHD1 is regulated by acetylation, which promotes cell cycle progression in cancer cells...
September 15, 2017: Oncotarget
Robin van der Lee, Laurens Wiel, Teunis J P van Dam, Martijn A Huynen
Hotspots of rapid genome evolution hold clues about human adaptation. We present a comparative analysis of nine whole-genome sequenced primates to identify high-confidence targets of positive selection. We find strong statistical evidence for positive selection in 331 protein-coding genes (3%), pinpointing 934 adaptively evolving codons (0.014%). Our new procedure is stringent and reveals substantial artefacts (20% of initial predictions) that have inflated previous estimates. The final 331 positively selected genes (PSG) are strongly enriched for innate and adaptive immunity, secreted and cell membrane proteins (e...
October 13, 2017: Nucleic Acids Research
Maria Jose Cabello-Lobato, Siyue Wang, Christine Katrin Schmidt
SAMHD1 (sterile α motif and histidine (H) aspartate (D) domain-containing protein 1) is known for its antiviral activity of hydrolysing deoxynucleotides required for virus replication. Daddacha et al. identify a hydrolase-independent, moonlighting function of SAMHD1 that facilitates homologous recombination of DNA double-strand breaks (DSBs) by promoting recruitment of C-terminal binding protein interacting protein (CTIP), a DNA-end resection factor, to damaged DNA. These findings could benefit anticancer treatment...
September 29, 2017: Trends in Genetics: TIG
Kajwal Kumar Patra, Akash Bhattacharya, Swati Bhattacharya
The sterile alpha motif and histidine-aspartate domain-containing protein 1 (or SAMHD1), a human dNTP-triphosphohydrolase, contributes to HIV-1 restriction in select terminally differentiated cells of the immune system. The catalytically active form of the protein is an allosterically triggered tetramer, whose HIV-1 restriction properties are attributed to its dNTP-triphosphohydrolase activity. The tetramer itself is assembled by a GTP/dNTP combination. This enzyme uses the strategy of deoxynucleotide starvation, which is thought to prevent effective reverse transcription of the retroviral genome-hence, restricting HIV-1 propagation...
October 23, 2017: Journal of Chemical Information and Modeling
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