Induced Packaging of Cellular MicroRNAs into HIV-1 Virions Can Inhibit Infectivity.

Hal P Bogerd,Bryan R Cullen,Edward M Kennedy,Adam W Whisnant,Stephen P Goff

doi:10.1128/mbio.02125-16

Abstract

ABSTRACTAnalysis of the incorporation of cellular microRNAs (miRNAs) into highly purified HIV-1 virions revealed that this largely, but not entirely, mirrored the level of miRNA expression in the producer CD4+ T cells. Specifically, of the 58 cellular miRNAs detected at significant levels in the producer cells, only 5 were found in virions at a level 2- to 4-fold higher than that predicted on the basis of random cytoplasmic sampling. Of note, these included two miRNAs, miR-155 and miR-92a, that were reported previously to at least weakly bind HIV-1 transcripts. To test whether miRNA binding to the HIV-1 genome can induce virion incorporation, artificial miRNA target sites were introduced into the viral genome and a 10- to 40-fold increase in the packaging of the cognate miRNAs into virions was then observed, leading to the recruitment of up to 1.6 miRNA copies per virion. Importantly, this high level of incorporation significantly inhibited HIV-1 virion infectivity. These results suggest that target sites for cellular miRNAs can inhibit RNA virus replication at two distinct steps, i.e., during infection and during viral gene expression, thus explaining why a range of different RNA viruses appear to have evolved to avoid cellular miRNA binding to their genome.

Highlights

Analysis of the incorporation of cellular microRNAs into highly purified HIV-1 virions revealed that this largely, but not entirely, mirrored the level of miRNA expression in the producer CD4ϩ T cells
Several groups have reported that a number of different cellular miRNAs bind to specific target sites located on the HIV-1 RNA genome and reduce viral gene expression [1,2,3], and it has even been suggested that cellular miRNAs can facilitate HIV-1 latency [4]
Consistent with the idea that HIV-1 has evolved to avoid the binding of miRNA-programed RNA induced silencing complex (RISC) to viral mRNAs, and any resultant translational repression and/or destabilization, we have demonstrated that blocking miRNA biogenesis entirely, by mutational inactivation of Dicer, does not detectably enhance the replication of HIV-1 or a wide range of other RNA viruses [10], a result confirmed by others [17]

Summary

Introduction

Analysis of the incorporation of cellular microRNAs (miRNAs) into highly purified HIV-1 virions revealed that this largely, but not entirely, mirrored the level of miRNA expression in the producer CD4ϩ T cells. The specific incorporation of high levels of individual cellular miRNAs can be induced by insertion of cognate target sites into the viral genome Of note, this results in a modest but significant inhibition of virion infectivity. This laboratory has reported that miRNA binding to HIV-1 transcripts, while detectable, is ~100-fold less efficient than miRNA binding to cellular mRNAs expressed contemporaneously in HIV-1-infected T cells [5] This finding is consistent with data demonstrating that the HIV-1 RNA genome is highly structured [6] and that RNA secondary structure inhibits miRNA binding, including to predicted miRNA binding sites present on HIV-1 transcripts [7,8,9]. MiRNA incorporation can be greatly enhanced by insertion into the HIV-1 RNA genome of partially complementary targets specific for individual cellular miRNAs, and this incorporation can significantly inhibit HIV-1 virion infectivity

Methods

Results

Conclusion