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The ribonuclease activity of SAMHD1 is required for HIV-1 restriction

ABSTRACT: SAMHD1 restricts HIV-1 replication in dendritic and other myeloid cells. SAMHD1 has been shown to possess a dGTP-dependent dNTP triphosphatase (dNTPase) activity and is proposed to inhibit HIV-1 replication by depleting the intracellular dNTP pool. Arguing against a role for SAMHD1 dNTPase in HIV-1 restriction, the phosphorylation of SAMHD1 regulates the restriction activity toward HIV-1 without affecting its ability to decrease cellular dNTP levels. Here, we show that SAMHD1 is a phospho-regulated RNase and that the RNase function is required for HIV-1 restriction. Mutation of the SAMHD1 D137 residue in the allosteric site (SAMHD1D137N) abolishes dNTPase activity but has no effect on RNase activity. This dNTPase-defective SAMHD1D137N mutant is able to restrict HIV-1 infection to nearly the same extent as wild-type SAMHD1. SAMHD1 associates with and degrades the HIV-1 genomic RNA during the early phases of infection. SAMHD1 silencing in macrophages and CD4+ T cells from healthy donors increases HIV-1 RNA stability, thus rendering the cells permissive for HIV-1 infection. Furthermore, the phosphorylation of SAMHD1 at position T592 abolishes the RNase activity toward HIV-1 RNA, and consequently the ability of SAMHD1 to restrict HIV-1 infection, uncovering the phosphorylation of SAMHD1 T592 as a negative regulatory mechanism of RNase activity. Together, our results demonstrate that SAMHD1 is an essential RNase that prevents HIV-1 infection by directly degrading HIV-1 genomic RNA in a phosphorylation-regulated manner. The unique property of SAMHD1 that cleaves HIV-1 genomic RNA with no sequence preferences could be exploited to develop a new class of intervention for error-prone retroviruses.

ORGANISM(S): Homo sapiens

PROVIDER: GSE58418 | GEO | 2014/06/13

SECONDARY ACCESSION(S): PRJNA252557

REPOSITORIES: GEO

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SAMHD1 is a phospho-regulated Rnase that is essential for restricting HIV-1 infection through direct cleavage of HIV-1 genomic RNA

Project description:SAMHD1 restricts HIV-1 replication in dendritic and other myeloid cells. SAMHD1 has been shown to possess a dGTP-dependent dNTP triphosphatase (dNTPase) activity and is proposed to inhibit HIV-1 replication by depleting the intracellular dNTP pool. Arguing against a role for SAMHD1 dNTPase in HIV-1 restriction, the phosphorylation of SAMHD1 regulates the restriction activity toward HIV-1 without affecting its ability to decrease cellular dNTP levels. Here, we show that SAMHD1 is a phospho-regulated RNase and that the RNase function is required for HIV-1 restriction. Mutation of the SAMHD1 D137 residue in the allosteric site (SAMHD1D137N) abolishes dNTPase activity but has no effect on RNase activity. This dNTPase-defective SAMHD1D137N mutant is able to restrict HIV-1 infection to nearly the same extent as wild-type SAMHD1. SAMHD1 associates with and degrades the HIV-1 genomic RNA during the early phases of infection. SAMHD1 silencing in macrophages and CD4+ T cells from healthy donors increases HIV-1 RNA stability, thus rendering the cells permissive for HIV-1 infection. Furthermore, the phosphorylation of SAMHD1 at position T592 abolishes the RNase activity toward HIV-1 RNA, and consequently the ability of SAMHD1 to restrict HIV-1 infection, uncovering the phosphorylation of SAMHD1 T592 as a negative regulatory mechanism of RNase activity. Together, our results demonstrate that SAMHD1 is an essential RNase that prevents HIV-1 infection by directly degrading HIV-1 genomic RNA in a phosphorylation-regulated manner. The unique property of SAMHD1 that cleaves HIV-1 genomic RNA with no sequence preferences could be exploited to develop a new class of intervention for error-prone retroviruses. Ribosomal RNA-depleted total RNA profiles of mock, SAMHD1 wild type and mutants infected with HIV-1 were examined at the time of 0, 1, 3 h by Illumina Hiseq2500.

2014-06-13 | E-GEOD-58418 | biostudies-arrayexpress

Guanine-containing ssDNA and RNA induce dimeric and tetrameric SAMHD1 in cryo-EM and binding studies

Project description:The dNTPase activity of tetrameric SAM and HD domain containing deoxynucleoside triphosphate triphosphohydrolase 1 (SAMHD1) plays a critical role in cellular dNTP regulation. SAMHD1 also associates with stalled DNA replication forks, DNA repair foci, ssRNA, and telomeres. The above functions require nucleic acid binding by SAMHD1, which may be modulated by its oligomeric state. Here we establish that the guanine-specific A1 activator site of each SAMHD1 monomer is used to target the enzyme to guanine nucleotides within single-stranded (ss) DNA and RNA. Remarkably, nucleic acid strands containing a single guanine base induce dimeric SAMHD1, while two or more guanines with ~20 nucleotide spacing induce a tetrameric form. A cryo-EM structure of ssRNA-bound tetrameric SAMHD1 shows how ssRNA strands bridge two SAMHD1 dimers and stabilize the structure. This ssRNA-bound tetramer is inactive with respect to dNTPase and RNase activity.

2023-11-13 | PXD043587 | Pride

Gene expression of fibroblasts carrying SAMHD1 mutations or not

Project description:In mammalian cells, the catabolic activity of the dNTP triphosphohydrolase SAMHD1 sets the balance and the concentrations of the four dNTPs. Deficiency of SAMHD1 leads to unequally increased pools and marked dNTP imbalance. Although it is documented that imbalanced dNTP pool expansion increases mutation frequency in cancer cells, it is not known if the SAMHD1-induced dNTP imbalance favors accumulation of somatic mutations in non-transformed cells. Here we have investigated how fibroblasts isolated 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, 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 than wildtype fibroblasts. To investigate if 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 non-transformed cells.

2019-12-03 | GSE135652 | GEO

Homo sapiens

Project description:The ribonuclease activity of SAMHD1 is required for HIV-1 restriction

| PRJNA252557 | ENA

Vpx of SIV modulates expression of innate immune target genes by inhibition of NF-κB activation

Project description:Background: In contrast to HIV-1, lentiviruses of the HIV-2/SIVmac/SIVsmm lineage are capable of efficient replication in myeloid cells due to the presence of their accessory protein Vpx. Vpx has been shown to induce degradation of the dNTP triphosphohydrolase SAMHD1, which is a cellular restriction factor of lentiviral replication. Furthermore, Vpx is important for nuclear import of the viral pre-integration complex. To identify further functions of Vpx, we have analyzed the effect of Vpx on cellular gene expression in monocytes. Therefore, we performed whole genome microarray analysis of unstimulated primary human monocytes treated with SIV–based virus-like particles containing Vpx (VLP+Vpx) or lacking Vpx (VLP). Results: Comparison of the gene expression profiles of human monocytes treated with VLP+Vpx and VLP revealed that Vpx down-regulates various genes involved in innate immunity, in particular genes that are known to be regulated by the transcription factor NF-κB. Subsequent analysis of p65 nuclear translocation revealed that Vpx inhibits the VLP-induced activation of NF-κB. Counteraction of NF-κB was also obtained using Vpx mutants lacking the capacity to induce SAMHD1 degradation. Conclusions: Independent of its capacity to induce degradation of SAMHD1, Vpx is involved in regulation of cellular gene expression. In particular, Vpx is able to modulate innate immune responses through down-regulation of TLR-induced NF-κB activation. This points to a significant role of Vpx in the pathogenicity of SIV, as the lower pathogenicity of SIV compared to HIV-1 has been associated to lower innate immunity responses.

2014-06-28 | GSE48542 | GEO

SAMHD1 restrains aberrant nucleotide insertions at repair junctions generated by DNA end joining

Project description:Aberrant end joining of DNA double strand breaks leads to chromosomal rearrangements and to insertion of nuclear or mitochondrial DNA into breakpoints, which is commonly observed in cancer cells and constitutes a major threat to genome integrity. However, the mechanisms that are causative for these insertions are largely unknown. By monitoring end joining of different linear DNA substrates introduced into HEK293 cells, as well as by examining end joining of CRISPR/Cas9 induced DNA breaks in HEK293 and HeLa cells, we provide evidence that the dNTPase activity of SAMHD1 impedes aberrant DNA resynthesis at DNA breaks during DNA end joining. Hence, SAMHD1 expression or low intracellular dNTP levels lead to shorter repair joints and impede insertion of distant DNA regions prior end repair. Our results reveal a novel role for SAMHD1 in DNA end joining and provide new insights into how loss of SAMHD1 may contribute to genome instability and cancer development.

2021-01-20 | E-MTAB-8382 | biostudies-arrayexpress

SAMHD1 degrades nascent DNA at stalled Forks to promote replication restart

Project description:SAMHD1 is a triphosphohydrolase and a 3'-5' exonuclease that restricts HIV-1 infection in non-cycling cells. It is also mutated in the Aicardi-Goutières Syndrome (AGS) and in different cancers, including chronic lymphotic leukemia. We report herre that SAMHD1 localizes to DNA replication foci during S phase suggesting that it is involved in DNA synthesis. Using microarray analysis, we examine the replication timing program an we show that SAMHD1 regulates the fork progression but also the replication timing program.

2017-07-29 | GSE77392 | GEO

Genome-scale CRISPR screen reveals inhibitory factors as regulatory module of HIV

Project description:To identify host factors that restrict HIV replication, we conducted a CRISPR activation screen in a susceptible T cell line using a high-complexity, genome-wide sgRNA library. Our results identified host factors that conferred protection from HIV infection.

2022-06-04 | GSE185343 | GEO

Next Generation Sequencing Facilitates Quantitative Analysis of HIV Elite controller, HIV ART, HIV ART-naive and healthy control Transcriptomes

Project description:A small group of HIV-1-infected individuals, termed elite controllers (ECs), display control of HIV replication in the absence of antiretroviral therapy (ART). However, the mechanisms of resistance to HIV in ECs remains largely unknown. To identify host factors specific to the ECs that might be involved in controlling HIV infection, we performed RNA-seq transcriptome analysis, and a total of 44 samples were included. The monocytes from each sample were enriched, sequenced, and subjected to comparative transcriptome analysis to screen candidate genes that might affect resistance to HIV infection. we found several candidate genes with highly divergent expression that might contribute to the different outcomes of HIV infection in ECs and non-ECs. This finding will help elucidate the mechanisms by which ECs restrict HIV replication and represents a new approach for treatment of HIV.

2021-12-09 | GSE157198 | GEO

Inhibition of HIV infection by structural proteins of the inner nuclear membrane is associated with reduced chromatin dynamics

Project description:The human immunodeficiency virus (HIV) enters the nucleus to establish infection, but the role of nuclear envelope proteins in this process is incompletely understood. Inner nuclear transmembrane proteins SUN1 and SUN2 connect nuclear lamins to the cytoskeleton and participate in the DNA damage response (DDR). Increased levels of SUN1 or SUN2 potently restrict HIV infection through an unresolved mechanism. Here, we find that the antiviral activities of SUN1 and SUN2 are distinct. HIV-1 and HIV-2 are preferentially inhibited by SUN1 and SUN2, respectively. We identify DNA damage inducers that stimulate HIV-1 infection and show that SUN1, but not SUN2, neutralizes this effect. Finally, we show that chromatin movements and nuclear rotations are associated with the effects of SUN proteins and Lamin A/C on infection. These results reveal an emerging role of chromatin dynamics and the DDR in the control of HIV infection by structural components of the nuclear envelope.

2022-03-16 | GSE162019 | GEO

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