Suppression of HIV-1 replication by microRNA effectors

Abstract

The rate of HIV-1 gene expression is a key step that determines the kinetics of virus spread and AIDS progression. Viral entry and gene expression were described to be the key determinants for cell permissiveness to HIV. Recent reports highlighted the involvement of miRNA in regulating HIV-1 replication post-transcriptionally. In this study we explored the role of cellular factors required for miRNA-mediated mRNA translational inhibition in regulating HIV-1 gene expression. Here we show that HIV-1 mRNAs associate and co-localize with components of the RNA Induced Silencing Complex (RISC), and we characterize some of the proteins required for miRNA-mediated silencing (miRNA effectors). RCK/p54, GW182, LSm-1 and XRN1 negatively regulate HIV-1 gene expression by preventing viral mRNA association with polysomes. Interestingly, knockdown of RCK/p54 or DGCR8 resulted in virus reactivation in PBMCs isolated from HIV infected patients treated with suppressive HAART.

RNAi and retroviruses: are they in RISC?

“…However, several independent studies have shown that DDX6 is required for PFV-1 (85) , HCV (86,87) , and HIV-1 (84) replication. This is in contrast with three other papers that reported that DDX6 either has no effect (88) or limits HIV-1 replication (58,63) . In fact, contradictory results have often been observed knocking down different RNAi-related components (Table 1).…”

“…In human cells, the RNA-binding protein ORF1 of the LINE-1 retrotransposon localizes with AGO2 and can physically interact with several of its partners (114) . These interactions have been proposed to mitigate the potential mutagenic effects of retrotransposition by sequestering LINE-1 ribonucleoproteins and possibly targeting them for degradation (114) , a scenario similar to that described for IAPs (115) and exogenous retroviruses (51,58,63) . Meanwhile, given that some components of the RNAi machinery have a dual role on the life cycle of exogenous retrovirus, it would be also worth investigating whether AGO2 and some of its partners can positively regulate LINE-1 ribonucleoprotein formation and retrotransposition.…”

“…These two types of interaction, which are not exclusive and are likely involved in distinct steps of the retroviral life cycle, are reminiscent of the dual interaction of AGO2 with HCV. The recognition of viral mRNAs by cellular miRNAs (51,57,58,63,83) and their sequestration in P bodies (58, 63) might thus represent the deleterious consequences of the recruitment of AGO2 or other RNAi-related components in viral replication. The mechanism by which AGO2 plays a positive role on retroviral replication is still poorly understood.…”

“…This process is thought to be similar to that described for endogenous miRNAs. It tethers the RNAi machinery, in particular AGO2, to viral messengers and leads to the sequestration of viral RNAs in P bodies and the inhibition of their translation (58,63) . Therefore, host miRNAs may have a potential as an RNA-based antiviral system (51, 54 -62, 64) .…”

The Lsm Proteins: Ring Architectures for RNA Capture

“…Specific RNA sequences recognized by various Lsm complexes include the Sm-site (A 2 U 5 GA) and U-rich stretches at the 3' end of oligoadenylated mRNA (Chowdhury et al, 2007) and RNA polymerase III transcripts, including snRNA (Achsel et al, 1999). Other binding partners include snoRNA (Kufel et al, 2003a), P RNA (Kufel et al, 2002), tRNA (Kufel et al, 2002) and rRNA (Kufel et al, 2003b).…”