Feline immunodeficiency virus Vif N-Terminal residues selectively counteract feline APOBEC3s

Feline immunodeficiency virus (FIV) Vif protein counteracts feline APOBEC3s (FcaA3s) restriction factors by inducing their proteasomal degradation. The functional domains in FIV Vif for interaction with FcaA3s are poorly understood. Here, we have identified several motifs in FIV Vif that are important for selective degradation of different FcaA3s. Cats (Felis catus) express three types of A3s: single-domain A3Z2, single-domain A3Z3, and double-domain A3Z2Z3. We proposed that FIV Vif would selectively interact with the Z2 and the Z3 A3s. Indeed, we identified two N-terminal Vif motifs (12LF13 and 18GG19) that specifically interacted with the FcaA3Z2 protein but not with A3Z3. In contrast, the exclusive degradation of FcaA3Z3 was regulated by a region of three residues (M24, L25, and I27). Only a FIV Vif carrying a combination of mutations from both interaction sites lost the capacity to degrade and counteract FcaA3Z2Z3. However, alterations in the specific A3s interaction sites did not affect the cellular localization of the FIV Vif protein and binding to feline A3s. Pulldown experiments demonstrated that the A3 binding region localized to FIV Vif residues 50 to 80, outside the specific A3 interaction domain. Finally, we found that the Vif sites specific to individual A3s are conserved in several FIV lineages of domestic cat and nondomestic cats, while being absent in the FIV Vif of pumas. Our data support a complex model of multiple Vif-A3 interactions in which the specific region for selective A3 counteraction is discrete from a general A3 binding domain

Experimental Study on Geopolymerization of Lunar Soil Simulant under Dry Curing and Sealed Curing

The construction of lunar surface roads is conducive to improving the efficiency of lunar space transportation. The use of lunar in situ resources is the key to the construction of lunar bases. In order to explore the strength development of a simulated lunar soil geopolymer at lunar temperature, geopolymers with different sodium hydroxide (NaOH) contents were prepared by using simulated lunar regolith materials. The temperature of the high-temperature section of the moon was simulated as the curing condition, and the difference in compressive strength between dry curing and sealed curing was studied. The results show that the high-temperature range of lunar temperature from 52.7 °C to 76.3 °C was the suitable curing period for the geopolymers, and the maximum strength of 72 h was 6.31 MPa when the NaOH content was 8% in the sealed-curing mode. The 72 h strength had a maximum value of 6.87 MPa when the NaOH content was 12% under dry curing. Choosing a suitable solution can reduce the consumption of activators required for geopolymers to obtain unit strength, effectively reduce the quality of materials transported from the Earth for lunar infrastructure construction, and save transportation costs. The microscopic results show that the simulated lunar soil generated gel substances and needle-like crystals under the alkali excitation of NaOH, forming a cluster and network structure to improve the compressive strength of the geopolymer

Energy Dissipation and Dynamic Fragmentation of Alkali-Activated Rubber Mortar under Multi-Factor Coupling Effect

Recycled rubber aggregate (RRA) made from ground tire rubber has been promoted for its light weight and shock resistance. The high alkalinity of alkali-activated slag mortar has a modification effect on the surface of RRA. This paper studies the performance of alkali-activated slag mortar using RRA as aggregate (RASM), which has significance for applications in low-carbon building materials. The orthogonal test analysis method was used to analyze the significance and correlation of the main variables of the test. The dynamic energy absorption capacity and crushing state of RASM under the synergistic effect of various factors were studied using the separating Hopkinson pressure bar (SHPB) test system. The energy absorption characteristics and failure modes of RASM were analyzed by SEM and microscopic pore characterization. The results show that the increase of the alkali equivalent of the mix ratio will increase the peak value of the absorption energy of the specimen. When the size of the RRA is between 0.48 mm~0.3 mm, the dynamic energy absorption of the specimen will reach its peak value. Although the increase in the total volume of RRA will reduce the energy absorption capacity of RASM specimens, its crack resistance is enhanced

Identification of a Conserved Interface of Human Immunodeficiency Virus Type 1 and Feline Immunodeficiency Virus Vifs with Cullin 5

The apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like (APOBEC3, A3) family of DNA cytidine deaminases are intrinsic restriction factors against retroviruses. In felids such as the domestic cat (Felis catus), the APOBEC3 (A3) genes encode for the A3Z2s, A3Z3, and A3Z2Z3 antiviral cytidine deaminases. Only A3Z3 and A3Z2Z3 inhibit viral infectivity factor (Vif)-deficient feline immunodeficiency virus (FIV). FIV Vif protein interacts with Cullin (CUL), Elongin B (ELOB), and Elongin C (ELOC) to form an E3 ubiquitination complex to induce the degradation of feline A3s. However, the functional domains in FIV Vif for interaction with Cullin are poorly understood. Here, we found that the expression of dominant-negative CUL5 prevented the degradation of feline A3s by FIV Vif, while dominant-negative CUL2 had no influence on the degradation of A3. In co-immunoprecipitation assays, FIV Vif bound to CUL5 but not CUL2. To identify the CUL5 interaction site in FIV Vif, the conserved amino acids from position 47 to 160 of FIV Vif were mutated, but these mutations did not impair the binding of Vif to CUL5. By focusing on a potential zinc-binding motif (K175— C161—C184—C187) of FIV Vif, we found a conserved hydrophobic region (174IR175) that is important for CUL5 interaction. Mutating this region also impaired the FIV Vif-induced degradation of feline A3s. Based on a structural model of the FIV Vif/CUL5 interaction, residues 52LW53 in CUL5 were identified as mediating the binding to FIV Vif. By comparing our results to the HIV-1 Vif/CUL5 interaction surface (120IR121, a hydrophobic region that is localized in the zinc-binding motif), we suggest that the CUL5 interaction surface in the diverse HIV-1 and FIV Vif is evolutionarily conserved indicating a strong structural constraint. However, the FIV Vif/CUL5 interaction is zinc-independent, which contrasts with the zinc-dependence of HIV-1 Vif

Feline immunodeficiency virus Vif N-Terminal residues selectively counteract feline APOBEC3s

Feline immunodeficiency virus (FIV) Vif protein counteracts feline APOBEC3s (FcaA3s) restriction factors by inducing their proteasomal degradation. The functional domains in FIV Vif for interaction with FcaA3s are poorly understood. Here, we have identified several motifs in FIV Vif that are important for selective degradation of different FcaA3s. Cats (Felis catus) express three types of A3s: single-domain A3Z2, single-domain A3Z3, and double-domain A3Z2Z3. We proposed that FIV Vif would selectively interact with the Z2 and the Z3 A3s. Indeed, we identified two N-terminal Vif motifs (12LF13 and 18GG19) that specifically interacted with the FcaA3Z2 protein but not with A3Z3. In contrast, the exclusive degradation of FcaA3Z3 was regulated by a region of three residues (M24, L25, and I27). Only a FIV Vif carrying a combination of mutations from both interaction sites lost the capacity to degrade and counteract FcaA3Z2Z3. However, alterations in the specific A3s interaction sites did not affect the cellular localization of the FIV Vif protein and binding to feline A3s. Pulldown experiments demonstrated that the A3 binding region localized to FIV Vif residues 50 to 80, outside the specific A3 interaction domain. Finally, we found that the Vif sites specific to individual A3s are conserved in several FIV lineages of domestic cat and nondomestic cats, while being absent in the FIV Vif of pumas. Our data support a complex model of multiple Vif-A3 interactions in which the specific region for selective A3 counteraction is discrete from a general A3 binding domain

Feline APOBEC3s, Barriers to Cross-Species Transmission of FIV?

The replication of lentiviruses highly depends on host cellular factors, which defines their species-specific tropism. Cellular restriction factors that can inhibit lentiviral replication were recently identified. Feline immunodeficiency virus (FIV) was found to be sensitive to several feline cellular restriction factors, such as apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3 (APOBEC3) and tetherin, but FIV evolved to counteract them. Here, we describe the molecular mechanisms by which feline APOBEC3 restriction factors inhibit FIV replication and discuss the molecular interaction of APOBEC3 proteins with the viral antagonizing protein Vif. We speculate that feline APOBEC3 proteins could explain some of the observed FIV cross-species transmissions described in wild Felids

Stably expressed APOBEC3H forms a barrier for cross-species transmission of simian immunodeficiency virus of chimpanzee to humans

APOBEC3s (A3s) are potent restriction factors of human immunodeficiency virus type 1/simian immunodeficiency viruses (HIV-1/SIV), and can repress cross-species transmissions of lentiviruses. HIV-1 originated from a zoonotic infection of SIV of chimpanzee (SIVcpz) to humans. However, the impact of human A3s on the replication of SIVcpz remains unclear. By using novel SIVcpz reporter viruses, we identified that human APOBEC3B (A3B) and APOBEC3H (A3H) haplotype II strongly reduced the infectivity of SIVcpz, because both of them are resistant to SIVcpz Vifs. We further demonstrated that human A3H inhibited SIVcpz by deaminase dependent as well independent mechanisms. In addition, other stably expressed human A3H haplotypes and splice variants showed strong antiviral activity against SIVcpz. Moreover, most SIV and HIV lineage Vif proteins could degrade chimpanzee A3H, but no Vifs from SIVcpz and SIV of gorilla (SIVgor) lineages antagonized human A3H haplotype II. Expression of human A3H hapII in human T cells efficiently blocked the spreading replication of SIVcpz. The spreading replication of SIVcpz was also restricted by stable A3H in human PBMCs. Thus, we speculate that stably expressed human A3H protects humans against the cross-species transmission of SIVcpz and that SIVcpz spillover to humans may have started in individuals that harbor haplotypes of unstable A3H proteins

Chimpanzee APOBEC3s (cpzA3s) inhibit SIVs.

<p>(<b>a, b</b>) SIVmac or SIVagm wild type or delta <i>vif</i> reporter viruses were produced in 293T cells in the presence of cpzA3s. pcDNA3.1(+) was used as control (vector) for cpzA3s. Two days post-transfection, normalized amounts of viruses were used to infect 293T cells, firefly luciferase (relative light units-RLU) was measured two days post-infection. (<b>c, d</b>) SIVcpz<i>Ptt</i>MB897 or SIVcpz<i>Pts</i>TAN1 wild type or delta <i>vif</i> reporter viruses were produced in 293T cells in the presence of cpzA3s. pcDNA3.1(+) was used as control (vector) for cpzA3s. Two days post-transfection, normalized amounts of viruses were used to infect 293T cells. Two days post-infection, 293T cells were carefully washed once with PBS, and nanoluciferase (relative light units-RLU) was measured, relative infectivity was shown. Values are means plus standard deviations (error bars) of a representative experiment performed in triplicate. Asterisks represent statistically significant differences: P value < 0.001 extremely significant (***), 0.001 to 0.01 very significant (**), 0.01 to 0.05 significant (*), >0.05 not significant (ns).</p

Human APOBEC3s (hA3s) inhibit SIVs.

<p>(<b>a, b</b>) SIVmac or SIVagm wild type or delta <i>vif</i> reporter viruses were produced in 293T cells in the presence of hA3s. PTR600 empty vector was used as control (vector) for hA3s. Two days post-transfection, normalized amounts of viruses were used to infect 293T cells, firefly luciferase (relative light units-RLU) was measured two days post-infection. (<b>c, d</b>) SIVcpz<i>Ptt</i>MB897 or SIVcpz<i>Pts</i>TAN1 wild type or delta <i>vif</i> reporter viruses were produced in 293T cells in the presence of hA3s. PTR600 empty vector was used as control (vector) for hA3s. Two days post-transfection, normalized amounts of viruses were used to infect 293T cells. Two days post-infection, 293T cells were carefully washed once with PBS, and nanoluciferase (relative light units-RLU) was measured. The relative infectivity was shown. Values are means plus standard deviations (error bars) of a representative experiment performed in triplicate. Asterisks represent statistically significant differences: P value < 0.001 extremely significant (***), 0.001 to 0.01 very significant (**), 0.01 to 0.05 significant (*), >0.05 not significant (ns).</p

Stable hA3H inhibits SIVcpz replication in human PBMCs.

<p>(<b>a</b>) The genotypes of different donors were determined by sequencing the A3H mRNAs. Expression of A3H and A3G proteins in stimulated PBMCs were detected by immunoblots using anti-hA3H and anti-hA3G antibodies, respectively. Tubulin served as a loading control. (<b>b, c</b>) PBMCs from different donors were infected with 1 ng RT or 5 ng RT activity of SIVcpz<i>Ptt</i>MB897, respectively, and culture supernatants were collected each 2–3 day and analyzed for the RT activity.</p