Phosphorylation of mouse SAMHD1 regulates its restriction of human immunodeficiency virus type 1 infection, but not murine leukemia virus infection

Wang, Feifei; Gelais, Corine St.; Silva, Suresh de; Zhang, Hong; Yang, Geng; Shepard, Caitlin; Kim, Baek; Yount, Jacob S.; Wu, Li

doi:10.1016/j.virol.2015.10.024

Cited by 27 publications

(43 citation statements)

References 45 publications

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“…The carboxyl-terminal domain of ISF1 is phosphorylated at Thr-634 by CDK1 and CDK2 (26,28). Phosphomimetic mutation prevented antiviral activity yet had little effect on phosphohydrolase activity, a property shared by the human homologue (19,22) and consistent with previous reports (26,28).…”

Section: Discussionsupporting

confidence: 89%

“…Phosphomimetic mutation prevented antiviral activity yet had little effect on phosphohydrolase activity, a property shared by the human homologue (19,22) and consistent with previous reports (26,28). This finding raised the possibility that SAMHD1 does not restrict HIV-1 solely by dNTP pool depletion.…”

Section: Discussionsupporting

confidence: 88%

“…To do this we immunoprecipitated SAMHD1 from lysates of activated mouse splenic T cells and analyzed it by mass spectrometry. The analysis showed phosphorylation at amino acids Ser-49, Thr-52, Ser-55, Thr-56, Thr-310, and Thr-634 with frequencies ranging from 21% to 56% (Table 1), in agreement with a previous report (28). transduced with lentiviral vectors encoding GFP, ISF1, ISF2, or mutated ISF1 (⌬625, T634A, T634E, and P635A).…”

Section: Phosphorylation Of Isf1 At Thr-634 Regulates Its Antiviralsupporting

confidence: 91%

“…The results showed that ISF1 and ISF2 restricted HIV-1. ⌬625, T634A, and P635A retained antiviral activity, whereas T634E was inactive, consistent with previous reports (26,28). To confirm the results, we generated single-cell clones from U937 cell lines transduced with retroviral vectors encoding each of the SAMHD1 constructs.…”

Section: Phosphorylation Of Isf1 At Thr-634 Regulates Its Antiviralsupporting

confidence: 87%

“…These included: ⌬625 in which the sequence encoded by exon 16 was deleted; T634E, which mimics phosphorylated SAMHD1; T634A, which cannot be phosphorylated, (26,28); P635A (Fig. 1A).…”

Section: Phosphorylation Of Isf1 At Thr-634 Regulates Its Antiviralmentioning

confidence: 99%

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A Highly Active Isoform of Lentivirus Restriction Factor SAMHD1 in Mouse

Bloch

Gläsker

Sitaram

et al. 2017

Journal of Biological Chemistry

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Edited by Henrik G. DohlmanThe triphosphohydrolase SAMHD1 (sterile ␣ motif and histidine-aspartate domain-containing protein 1) restricts HIV-1 replication in nondividing myeloid cells by depleting the dNTP pool, preventing reverse transcription. SAMHD1 is also reported to have ribonuclease activity that degrades the virus genomic RNA. Human SAMHD1 is regulated by phosphorylation of its carboxyl terminus at Thr-592, which abrogates its antiviral function yet has only a small effect on its phosphohydrolase activity. In the mouse, SAMHD1 is expressed as two isoforms (ISF1 and ISF2) that differ at the carboxyl terminus due to alternative splicing of the last coding exon. In this study we characterized the biochemical and antiviral properties of the two mouse isoforms of SAMHD1. Both are antiviral in nondividing cells. Mass spectrometry analysis showed that SAMHD1 is phosphorylated at several amino acid residues, one of which (Thr-634) is homologous to Thr-592. Phosphomimetic mutation at Thr-634 of ISF1 ablates its antiviral activity yet has little effect on phosphohydrolase activity in vitro. dGTP caused ISF1 to tetramerize, activating its catalytic activity. In contrast, ISF2, which lacks the phosphorylation site, was significantly more active, tetramerized, and was active without added dGTP. Neither isoform nor human SAMHD1 had detectable RNase activity in vitro or affected HIV-1 genomic RNA stability in newly infected cells. These data support a model in which SAMHD1 catalytic activity is regulated through tetramer stabilization by the carboxyl-terminal tail, phosphorylation destabilizing the complexes and inactivating the enzyme. ISF2 may serve to reduce the dNTP pool to very low levels as a means of restricting virus replication. The lentiviral restriction factor SAMHD12 is a dNTP triphosphohydrolase (1, 2) that inhibits the replication of HIV-1 in myeloid cells (3, 4). The enzyme removes the triphosphate groups of dNTPs, preventing the reverse transcription in newly infected cells (5). In addition, SAMHD1 has been proposed to have ribonuclease activity that degrades the viral genomic RNA upon virus entry (6). HIV-2 and some SIVs counteract the restriction by encoding Vpx, a virion-packaged accessory protein that induces the proteasomal degradation of SAMHD1 (3, 4, 7). Other SIVs, such as the SIV of African green monkeys, counteract SAMHD1 through the related accessory protein Vpr (8, 9). Vpx delivery into the cell by virions causes a rapid rise in the intracellular dNTP concentration, relieving the block to reverse transcription and allowing productive infection (5, 10). HIV-1 does not encode Vpx and as a result replicates poorly in dendritic and other myeloid cells. The requirement for Vpx for infection of myeloid cells can be partially replaced in culture by the addition of extracellular deoxynucleosides, which are converted into dNTPs by the salvage pathway (5). In addition, HIV-1 can be genetically modified to package Vpx, allowing it to infect myeloid cells (11,12).The catalytic activity of SAMHD1 is reg...

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Section: Discussionsupporting

confidence: 89%

Section: Discussionsupporting

confidence: 88%

Section: Phosphorylation Of Isf1 At Thr-634 Regulates Its Antiviralsupporting

confidence: 91%

Section: Phosphorylation Of Isf1 At Thr-634 Regulates Its Antiviralsupporting

confidence: 87%

“…These included: ⌬625 in which the sequence encoded by exon 16 was deleted; T634E, which mimics phosphorylated SAMHD1; T634A, which cannot be phosphorylated, (26,28); P635A (Fig. 1A).…”

Section: Phosphorylation Of Isf1 At Thr-634 Regulates Its Antiviralmentioning

confidence: 99%

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