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The human antiviral factor TRIM11 is under the regulation of HIV-1 Vpr.

Yuan T, Yao W, Huang F, Sun B, Yang R - PLoS ONE (2014)

Bottom Line: In this study, we demonstrated that TRIM11 mainly suppressed the early steps of HIV-1 transduction, resulting in decreased reverse transcripts.Additionally, we found that TRIM11 could inhibit HIV-1 long terminal repeat (LTR) activity, which may be related to its inhibitory effects on NF-κB.These results suggest that the antiviral factor TRIM11 is indirectly regulated by HIV-1 Vpr through unknown mechanisms and that the concentration of Vpr is essential to these processes.

View Article: PubMed Central - PubMed

Affiliation: Research Group of HIV Molecular Epidemiology and Virology, Center for Emerging Infectious Diseases, The State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, The People's Republic of China.

ABSTRACT
TRIM11 has been reported to be able to restrict HIV-1 replication, but the detailed aspects of the interfering mechanisms remain unclear. In this study, we demonstrated that TRIM11 mainly suppressed the early steps of HIV-1 transduction, resulting in decreased reverse transcripts. Additionally, we found that TRIM11 could inhibit HIV-1 long terminal repeat (LTR) activity, which may be related to its inhibitory effects on NF-κB. Deletion mutant experiments showed that the RING domain of TRIM11 was indispensable in inhibiting the early steps of HIV-1 transduction but was dispensable in decreasing NF-κB and LTR activities. Moreover, we found that low levels of Vpr decreased TRIM11 protein levels, while high levels increased them, and these regulations were independent of the VprBP-associated proteasome machinery. These results suggest that the antiviral factor TRIM11 is indirectly regulated by HIV-1 Vpr through unknown mechanisms and that the concentration of Vpr is essential to these processes. Thus, our work confirms TRIM11 as a host cellular factor that interferes with the early steps of HIV-1 replication and provides a connection between viral protein and host antiviral factors.

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Interactions between TRIM11 and Vpr or VprBP.HEK293 cells were cotransfected with the indicated combinations of expression vectors (TRIM11-Myc, Vpr-Flag and VprBP-HA). Twenty-four hours post-infection cell lysates were immunoprecipitated and immunoblotted with the indicated antibodies. Representative results from three separate experiments are shown.
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pone-0104269-g006: Interactions between TRIM11 and Vpr or VprBP.HEK293 cells were cotransfected with the indicated combinations of expression vectors (TRIM11-Myc, Vpr-Flag and VprBP-HA). Twenty-four hours post-infection cell lysates were immunoprecipitated and immunoblotted with the indicated antibodies. Representative results from three separate experiments are shown.

Mentions: Recently, the fact that Vpr is able to bridge the proteasome to degrade a variety of substrates by binding to the E3 ubiquitin ligase complex has attracted attention [27]–[29]. Vpr binding protein (VprBP), which is also known as DDB1-Cul4A associated factor 1 (DCAF1), acts as an adaptor to link Vpr to the CUL ubiquitin E3 ligase system [41], [42]. Several proteins, including UNG2 and SMUG1, have been reported to be targets of Vpr through this proteasome system [27], [28]. We therefore tested whether Vpr or VprBP could interact with TRIM11 by co-immunoprecipitation. As shown in Figure 6, we failed to see any interaction between TRIM11 and either Vpr or VprBP. The interaction between Vpr and VprBP was used as a positive control to assess the experimental system. Thus, we deduced that Vpr may indirectly regulate TRIM11 protein levels. To determine whether this regulation was dependent on the ubiquitin system or VprBP-mediated pathway as the degradation of UNG2 and SMUG1 by Vpr, we first assessed the effects of different amounts of Vpr on TRIM11 following DMSO or MG132 treatments. In accordance with the above results, Vpr was able to down-regulate TRIM11 protein levels at lower concentrations, and up-regulate these levels at higher concentrations (Figure 7A). However, we failed to see significant differences in TRIM11 protein levels following treatment with DMSO or MG132 when Vpr was expressed at different concentrations (Figure 7A). In addition, TRIM11 protein levels profoundly increase following MG132 treatment in the absence of Vpr (Figure 7A), indicating that its protein levels may have been in a balance between degradation and synthesis, similar to other TRIM family members [43]. These results suggest that the regulation of TRIM11 by Vpr may be independent of the ubiquitin system. Furthermore, we tested the effects of VprBP on the regulation of TRIM11 by Vpr. We constructed another knockdown cell line stably expressing shRNA that targeted VprBP. Then, we cotransfected Myc-TRIM11 and different amounts of Vpr into a VprBP-knockdown cell line and control cell line expressing shRNA for GFP. As shown in Figure 7B, the knockdown of VprBP did not compromise the regulation of Vpr on TRIM11. In contrast, TRIM11 protein levels mildly increased in the VprBP-knockdown cell line and were irrelevant to Vpr expression (Figure 7B). Together, these results suggest that Vpr may indirectly regulate TRIM11 in a concentration-related manner, which is independent of the ubiquitin system or VprBP-mediated pathway.


The human antiviral factor TRIM11 is under the regulation of HIV-1 Vpr.

Yuan T, Yao W, Huang F, Sun B, Yang R - PLoS ONE (2014)

Interactions between TRIM11 and Vpr or VprBP.HEK293 cells were cotransfected with the indicated combinations of expression vectors (TRIM11-Myc, Vpr-Flag and VprBP-HA). Twenty-four hours post-infection cell lysates were immunoprecipitated and immunoblotted with the indicated antibodies. Representative results from three separate experiments are shown.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126725&req=5

pone-0104269-g006: Interactions between TRIM11 and Vpr or VprBP.HEK293 cells were cotransfected with the indicated combinations of expression vectors (TRIM11-Myc, Vpr-Flag and VprBP-HA). Twenty-four hours post-infection cell lysates were immunoprecipitated and immunoblotted with the indicated antibodies. Representative results from three separate experiments are shown.
Mentions: Recently, the fact that Vpr is able to bridge the proteasome to degrade a variety of substrates by binding to the E3 ubiquitin ligase complex has attracted attention [27]–[29]. Vpr binding protein (VprBP), which is also known as DDB1-Cul4A associated factor 1 (DCAF1), acts as an adaptor to link Vpr to the CUL ubiquitin E3 ligase system [41], [42]. Several proteins, including UNG2 and SMUG1, have been reported to be targets of Vpr through this proteasome system [27], [28]. We therefore tested whether Vpr or VprBP could interact with TRIM11 by co-immunoprecipitation. As shown in Figure 6, we failed to see any interaction between TRIM11 and either Vpr or VprBP. The interaction between Vpr and VprBP was used as a positive control to assess the experimental system. Thus, we deduced that Vpr may indirectly regulate TRIM11 protein levels. To determine whether this regulation was dependent on the ubiquitin system or VprBP-mediated pathway as the degradation of UNG2 and SMUG1 by Vpr, we first assessed the effects of different amounts of Vpr on TRIM11 following DMSO or MG132 treatments. In accordance with the above results, Vpr was able to down-regulate TRIM11 protein levels at lower concentrations, and up-regulate these levels at higher concentrations (Figure 7A). However, we failed to see significant differences in TRIM11 protein levels following treatment with DMSO or MG132 when Vpr was expressed at different concentrations (Figure 7A). In addition, TRIM11 protein levels profoundly increase following MG132 treatment in the absence of Vpr (Figure 7A), indicating that its protein levels may have been in a balance between degradation and synthesis, similar to other TRIM family members [43]. These results suggest that the regulation of TRIM11 by Vpr may be independent of the ubiquitin system. Furthermore, we tested the effects of VprBP on the regulation of TRIM11 by Vpr. We constructed another knockdown cell line stably expressing shRNA that targeted VprBP. Then, we cotransfected Myc-TRIM11 and different amounts of Vpr into a VprBP-knockdown cell line and control cell line expressing shRNA for GFP. As shown in Figure 7B, the knockdown of VprBP did not compromise the regulation of Vpr on TRIM11. In contrast, TRIM11 protein levels mildly increased in the VprBP-knockdown cell line and were irrelevant to Vpr expression (Figure 7B). Together, these results suggest that Vpr may indirectly regulate TRIM11 in a concentration-related manner, which is independent of the ubiquitin system or VprBP-mediated pathway.

Bottom Line: In this study, we demonstrated that TRIM11 mainly suppressed the early steps of HIV-1 transduction, resulting in decreased reverse transcripts.Additionally, we found that TRIM11 could inhibit HIV-1 long terminal repeat (LTR) activity, which may be related to its inhibitory effects on NF-κB.These results suggest that the antiviral factor TRIM11 is indirectly regulated by HIV-1 Vpr through unknown mechanisms and that the concentration of Vpr is essential to these processes.

View Article: PubMed Central - PubMed

Affiliation: Research Group of HIV Molecular Epidemiology and Virology, Center for Emerging Infectious Diseases, The State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, The People's Republic of China.

ABSTRACT
TRIM11 has been reported to be able to restrict HIV-1 replication, but the detailed aspects of the interfering mechanisms remain unclear. In this study, we demonstrated that TRIM11 mainly suppressed the early steps of HIV-1 transduction, resulting in decreased reverse transcripts. Additionally, we found that TRIM11 could inhibit HIV-1 long terminal repeat (LTR) activity, which may be related to its inhibitory effects on NF-κB. Deletion mutant experiments showed that the RING domain of TRIM11 was indispensable in inhibiting the early steps of HIV-1 transduction but was dispensable in decreasing NF-κB and LTR activities. Moreover, we found that low levels of Vpr decreased TRIM11 protein levels, while high levels increased them, and these regulations were independent of the VprBP-associated proteasome machinery. These results suggest that the antiviral factor TRIM11 is indirectly regulated by HIV-1 Vpr through unknown mechanisms and that the concentration of Vpr is essential to these processes. Thus, our work confirms TRIM11 as a host cellular factor that interferes with the early steps of HIV-1 replication and provides a connection between viral protein and host antiviral factors.

Show MeSH