Dataset Information

Production of HIV-1 vif mRNA Is Modulated by Natural Nucleotide Variations and SLSA1 RNA Structure in SA1D2prox Genomic Region.

ABSTRACT: Genomic RNA of HIV-1 contains localized structures critical for viral replication. Its structural analysis has demonstrated a stem-loop structure, SLSA1, in a nearby region of HIV-1 genomic splicing acceptor 1 (SA1). We have previously shown that the expression level of vif mRNA is considerably altered by some natural single-nucleotide variations (nSNVs) clustering in SLSA1 structure. In this study, besides eleven nSNVs previously identified by us, we totally found nine new nSNVs in the SLSA1-containing sequence from SA1, splicing donor 2, and through to the start codon of Vif that significantly affect the vif mRNA level, and designated the sequence SA1D2prox (142 nucleotides for HIV-1 NL4-3). We then examined by extensive variant and mutagenesis analyses how SA1D2prox sequence and SLSA1 secondary structure are related to vif mRNA level. While the secondary structure and stability of SLSA1 was largely changed by nSNVs and artificial mutations introduced to restore the original NL4-3 form from altered ones by nSNVs, no clear association of the two SLSA1 properties with vif mRNA level was observed. In contrast, when naturally occurring SA1D2prox sequences that contain multiple nSNVs were examined, we attained significant inverse correlation between the vif level and SLSA1 stability. These results may suggest that SA1D2prox sequence adapts over time, and also that the altered SA1D2prox sequence, SLSA1 stability, and vif level are mutually related. In total, we show here that the entire SA1D2prox sequence and SLSA1 stability critically contribute to the modulation of vif mRNA level.

SUBMITTER: Nomaguchi M

PROVIDER: S-EPMC5741601 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Production of HIV-1 <i>vif</i> mRNA Is Modulated by Natural Nucleotide Variations and SLSA1 RNA Structure in SA1D2prox Genomic Region.

Nomaguchi Masako M Doi Naoya N Yoshida Tomoya T Koma Takaaki T Adachi Shun S Ode Hirotaka H Iwatani Yasumasa Y Yokoyama Masaru M Sato Hironori H Adachi Akio A

Frontiers in microbiology 20171218

Genomic RNA of HIV-1 contains localized structures critical for viral replication. Its structural analysis has demonstrated a stem-loop structure, SLSA1, in a nearby region of HIV-1 genomic splicing acceptor 1 (SA1). We have previously shown that the expression level of <i>vif</i> mRNA is considerably altered by some natural single-nucleotide variations (nSNVs) clustering in SLSA1 structure. In this study, besides eleven nSNVs previously identified by us, we totally found nine new nSNVs in the S ...[more]

PMID: 29326677

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Project description:UnlabelledWe previously found that natural single-nucleotide variations located within a proximal region of splicing acceptor 1 (SA1prox) in the HIV-1 genome could alter the viral replication potential and mRNA expression pattern, especially the vif mRNA level. Here, we studied the virological and molecular basis of nucleotide sequence variations in SA1prox for alterations of viral replication ability. Consistent with our previous findings, variant clones indeed expressed Vif at different levels and grew distinctively in cells with various APOBEC3G expression levels. Similar effects were observed for natural variations found in HIV-2 SA1prox, suggesting the importance of the SA1prox sequence. To define nucleotides critical for the regulation of HIV-1 Vif expression, effects of natural SA1prox variations newly found in the HIV Sequence Compendium database on vif mRNA/Vif protein levels were examined. Seven out of nine variations were found to produce Vif at lower, higher, or more excessive levels than wild-type NL4-3. Combination experiments of variations giving distinct Vif levels suggested that the variations mutually affected vif transcript production. While low and high producers of Vif grew in an APOBEC3G-dependent manner, excessive expressers always showed an impeded growth phenotype due to defects in single-cycle infectivity and/or virion production levels. The phenotype of excessive expressers was not due primarily to inadequate expression of Tat or Rev, although SA1prox variations altered the overall HIV-1 mRNA expression pattern. Collectively, our results demonstrate that HIV SA1prox regulates Vif expression levels and suggest a relationship between SA1prox and viral adaptation/evolution given that variations occurred naturally.ImportanceWhile human cells possess restriction factors to inhibit HIV-1 replication, HIV-1 encodes antagonists to overcome these barriers. Conflicts between host restriction factors and viral counterparts are critical driving forces behind mutual evolution. The interplay of cellular APOBEC3G and viral Vif proteins is a typical example. Here, we demonstrate that naturally occurring single-nucleotide variations in the proximal region of splicing acceptor 1 (SA1prox) of the HIV-1 genome frequently alter Vif expression levels, thereby modulating viral replication potential in cells with various ABOBEC3G levels. The results of the present study reveal a previously unidentified and important way for HIV-1 to compete with APOBEC3G restriction by regulating its Vif expression levels. We propose that SA1prox plays a regulatory role in Vif counteraction against APOBEC3G in order to contribute to HIV-1 replication and evolution, and this may be applicable to other primate lentiviruses.

Project description:The virion infectivity factor (Vif) open reading frame is conserved among most lentiviruses. Vif molecules contribute to viral replication by inactivating host antiviral factors, the APOBEC3 cytidine deaminases. However, various species of lentiviral Vif proteins have evolved different strategies for overcoming host APOBEC3. Whether different species of lentiviral Vif proteins still preserve certain common features has not been reported. Here, we show for the first time that diverse lentiviral Vif molecules maintain the ability to interact with the human immunodeficiency virus type 1 (HIV-1) Gag precursor (Pr55Gag) polyprotein. Surprisingly, bovine immunodeficiency virus (BIV) Vif, but not HIV-1 Vif, interfered with HIV-1 production and viral infectivity even in the absence of APOBEC3. Further analysis revealed that BIV Vif demonstrated an enhanced interaction with Pr55Gag compared to that of HIV-1 Vif, and BIV Vif defective for the Pr55Gag interaction lost its ability to inhibit HIV-1. The C-terminal region of capsid (CA) and the p2 region of Pr55Gag, which are important for virus assembly and maturation, were involved in the interaction. Transduction of CD4+ T cells with BIV Vif blocked HIV-1 replication. Thus, the conserved Vif-Pr55Gag interaction provides a potential target for the future development of antiviral strategies.IMPORTANCE The conserved Vif accessory proteins of primate lentiviruses HIV-1, simian immunodeficiency virus (SIV), and BIV all form ubiquitin ligase complexes to target host antiviral APOBEC3 proteins for degradation, with different cellular requirements and using different molecular mechanisms. Here, we demonstrate that BIV Vif can interfere with HIV-1 Gag maturation and suppress HIV-1 replication through interaction with the precursor of the Gag (Pr55Gag) of HIV-1 in virus-producing cells. Moreover, the HIV-1 and SIV Vif proteins are conserved in terms of their interactions with HIV-1 Pr55Gag although HIV-1 Vif proteins bind Pr55Gag less efficiently than those of BIV Vif. Our research not only sheds new light on this feature of these conserved lentiviral Vif proteins but also provides a formerly unrecognized target for the development of antiviral strategies. Since increasing the Vif-Pr55Gag interaction could potentially suppress virus proliferation, this approach could offer a new strategy for the development of HIV inhibitors.

Project description:We previously showed that prototype macaque-tropic human immunodeficiency virus type 1 (HIV-1) acquired nonsynonymous growth-enhancing mutations within a narrow genomic region during the adaptation process in macaque cells. These adaptive mutations were clustered in the 3' region of the pol gene, encoding a small portion of the C-terminal domain of integrase (IN). Mutations in HIV-1 IN have been reported to have pleiotropic effects on both the early and late phases in viral replication. cis-acting functions in the IN-coding sequence for viral gene expression have also been reported. We here demonstrated that the adaptive mutations promoted viral growth by increasing virion production with no positive effects on the early replication phase. Synonymous codon alterations in one of the adaptive mutations influenced virion production levels, which suggested nucleotide-dependent regulation. Indeed, when the single-nucleotide natural polymorphisms observed in the 3' regions of 196 HIV-1/simian immunodeficiency virus (SIVcpz) pol genes (nucleotides [nt] 4895 to 4929 for HIV-1 NL4-3) were introduced into macaque- and human-tropic HIV-1 clones, more than half exhibited altered replication potentials. Moreover, single-nucleotide mutations caused parallel increases or decreases in the expression levels of viral late proteins and viral replication potentials. We also showed that the overall expression profiles of viral mRNAs were markedly changed by single-nucleotide mutations. These results demonstrate that the 3' region of the HIV-1 pol gene (nt 4895 to 4929) can alter viral replication potential by modulating the expression pattern of viral mRNAs in a nucleotide-dependent manner.Viruses have the plasticity to adapt themselves under various constraints. HIV-1 can mutate and evolve in growth-restrictive cells by acquiring adaptive changes in its genome. We have previously identified some growth-enhancing mutations in a narrow region of the IN-coding sequence, in which a number of cis-acting elements are located. We now focus on the virological significance of this pol gene region and the mechanistic basis underlying its effects on viral replication. We have found several naturally occurring synonymous mutations within this region that alter viral replication potentials. The effects caused by these natural single-nucleotide polymorphisms are linked to the definite expression patterns of viral mRNAs. We show here that the nucleotide sequence of the pol gene (nucleotides 4895 to 4929 for HIV-1 NL4-3) plays an important role in HIV-1 replication by modulating viral gene expression.

Dataset Information

Production of HIV-1 vif mRNA Is Modulated by Natural Nucleotide Variations and SLSA1 RNA Structure in SA1D2prox Genomic Region.

Publications

Production of HIV-1 <i>vif</i> mRNA Is Modulated by Natural Nucleotide Variations and SLSA1 RNA Structure in SA1D2prox Genomic Region.

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