Dataset Information

Gene expression of fibroblasts carrying SAMHD1 mutations or not

ABSTRACT: 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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE135652 | GEO | 2019/12/03

REPOSITORIES: GEO

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Project description:Although HIV-1 can directly infect resting CD4+ T cells, virus replication in resting CD4+T cells is very inefficient owing to the different host restriction factors blocking viral replication. The accessory protein Vpx from the major simian immunodeficiency virus (SIV) of rhesus macaque (mac) and HIV-2 lineage could degrade a host restriction factor, SAM and HD domain containing protein 1 (SAMHD1), to facilitate HIV reverse transcription. Interestingly, Vpx proteins from a second SIV lineage, the SIV of redcapped mangabeys or mandrills (SIVrcm/nmd-2), had no effect on SAMHD1 and did not affect the dNTP pool, but strongly increased HIV-1 infection in resting CD4+ T cells although not in primary macrophages. This indicates that Vpx, in addition to SAMHD1,can overcome a previously unexplored restriction factor for lentiviruses. Here to identify this potential restriction factor, we examined Vpxrcm-interacting cellular proteins and found that keratin 72 (KRT72), an intermediate filament protein that is exclusively expressed in resting CD4+ T cells, is a new host antiviral factor targeted by Vpx. Other than Vpx from SIV mac and HIV-2, the Vpxrcm/nmd-2 lineage, which had no effect on the SAMHD1 protein, could strongly promote the degradation of KRT72, resulting in enhanced HIV-1 infection in resting CD4+ T cells. Furthermore, we discovered that KRT72 restricts HIV-1 replication by sequestering incoming HIV-1 capsids in cytoplasmic intermediate filaments (IFs). In the presence of KRT72, HIV-1 capsid cores become attached to the IF and their trafficking toward the nucleus is inhibited. In contrast, in the absence of KRT72, HIV-1 capsids are transported into the nucleus,leading to high levels of integrated HIV-1 DNA. In addition, KRT72 expression was substantially higher in resting CD4+ T cells than in activated CD4+ T cells, and it was rapidly reduced by T cell activation. Collectively, the results show that KRT72 is a new Vpx-counteracted host antiviral factor that acts to tether incoming capsids to the cytoplasmic IF, thereby restricting HIV-1 infection in resting CD4+ T cells.