Emerman, M. | bioRxiv Science

bioRxiv2018

A Virus-Packageable CRISPR Screen Identifies Host Factors Mediating Interferon Inhibition of HIV

Interferon (IFN) inhibits HIV replication by inducing an array of antiviral effectors. Here we describe a novel CRISPR knockout screening approach to identify the ensemble of these HIV restriction factors. We assembled a CRISPR sgRNA library specific for Interferon Stimulated Genes (ISGs) into a modified lentiviral vector that allows for packaging of sgRNA-encoding genomes in trans into budding HIV-1 particles. We observed that knockout of Zinc Antiviral Protein (ZAP) improved the performance of the screen due to ZAP-mediated inhibition of the vector. We identify a small panel of IFN-induced HIV restriction factors, including MxB, IFITM1, Tetherin/BST2 and TRIM5 which together explain the inhibitory effects of IFN on the HIV-1 LAI strain in THP-1 cells. Further, we identify novel HIV dependency factors, including SEC62 and TLR2. The ability of IFN-induced restriction factors to inhibit an HIV strain to replicate in human cells suggests that these human restriction factors are incompletely antagonized.

microbiology↗

bioRxiv2018

Recurrent Loss of APOBEC3H Activity during Primate Evolution

Genes in the APOBEC3 family encode cytidine deaminases that provide a barrier against viral infection and retrotransposition. Of all APOBEC3 genes in humans, APOBEC3H (A3H) is the most polymorphic: some haplotypes encode stable and active A3H proteins, while others are unstable and inactive. Such variation in human A3H affects interactions with the lentiviral antagonist Vif, which counteracts A3H via proteasomal degradation. In order to broaden our understanding of A3H-Vif interactions as well as its evolution in Old World monkeys, we characterized A3H variation within four African green monkey (AGM) subspecies. We found that A3H is highly polymorphic in AGMs and has lost antiviral activity in multiple Old World monkeys. This loss of function was partially related to protein expression levels but was also influenced by amino acid mutations in the N-terminus. Moreover, we demonstrate that the evolution of A3H in the primate lineages leading to AGMs was not driven by Vif. Our work suggests that activity of A3H is evolutionarily dynamic and may have a negative effect on host fitness, resulting in its recurrent loss in primates.\n\nImportanceAdaptation of viruses to their hosts is critical for transmission of viruses between different species. Previous studies had identified changes in a protein from the APOBEC3 family that influenced species-specificity of simian immunodeficiency viruses (SIVs) in African green monkeys. We studied the evolution of a related protein in the same system, APOBEC3H, which has experienced a loss of function in humans. This evolutionary approach revealed that recurrent loss of APOBEC3H activity has taken place during primate evolution suggesting that APOBEC3H places a fitness cost on hosts. The variability of APOBEC3H activity between different primates highlights the differential selective pressures on the APOBEC3 gene family.

microbiology↗