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N-6-methyladenosine modification of HIV-1 RNA suppresses type-I interferon induction in differentiated monocytic cells and primary macrophages
Journal article   Open access   Peer reviewed

N-6-methyladenosine modification of HIV-1 RNA suppresses type-I interferon induction in differentiated monocytic cells and primary macrophages

Shuliang Chen, Sameer Kumar, Constanza E Espada, Nagaraja Tirumuru, Michael P Cahill, Lulu Hu, Chuan He and Li Wu
PLoS pathogens, Vol.17(3), p.e1009421
03/01/2021
DOI: 10.1371/journal.ppat.1009421
PMCID: PMC7984636
PMID: 33690734
url
https://doi.org/10.1371/journal.ppat.1009421View
Published (Version of record) Open Access

Abstract

Author summary HIV-1 is known as a weak inducer of antiviral cytokines including IFN-I, but it is unclear how HIV-1 evades innate immunity. Different types of RNA modifications including m(6)A within the HIV-1 genome modulate viral replication; however, the role of m(6)A modifications of HIV-1 RNA in regulating innate immune responses remains elusive. Myeloid cells including macrophages are HIV-1 target cells and critical for generating antiviral immunity. In this study, we aimed to investigate the role of m(6)A modifications of HIV-1 RNA in regulating innate immune responses in myeloid cells. We found that m(6)A-modified HIV-1 RNA suppresses IFN-I expression in differentiated monocytic cells and primary macrophages. Our data suggest that the cellular protein RIG-I contributes to innate sensing of m(6)A-defective HIV-1 RNA in differentiated monocytic cells. Our findings provide new insights into the functions and mechanisms of m(6)A modifications of HIV-1 RNA in regulating innate immune sensing and responses in myeloid cells. N-6-methyladenosine (m(6)A) is a prevalent RNA modification that plays a key role in regulating eukaryotic cellular mRNA functions. RNA m(6)A modification is regulated by two groups of cellular proteins, writers and erasers that add or remove m(6)A, respectively. HIV-1 RNA contains m(6)A modifications that modulate viral infection and gene expression in CD4(+) T cells. However, it remains unclear whether m(6)A modifications of HIV-1 RNA modulate innate immune responses in myeloid cells that are important for antiviral immunity. Here we show that m(6)A modification of HIV-1 RNA suppresses the expression of antiviral cytokine type-I interferon (IFN-I) in differentiated human monocytic cells and primary monocyte-derived macrophages. Transfection of differentiated monocytic U937 cells with HIV-1 RNA fragments containing a single m(6)A-modification significantly reduced IFN-I mRNA expression relative to their unmodified RNA counterparts. We generated HIV-1 with altered m(6)A levels of RNA by manipulating the expression of the m(6)A erasers (FTO and ALKBH5) or pharmacological inhibition of m(6)A addition in virus-producing cells, or by treating HIV-1 RNA with recombinant FTO in vitro. HIV-1 RNA transfection or viral infection of differentiated U937 cells and primary macrophages demonstrated that HIV-1 RNA with decreased m(6)A levels enhanced IFN-I expression, whereas HIV-1 RNA with increased m(6)A modifications had opposite effects. Our mechanistic studies indicated that m(6)A of HIV-1 RNA escaped retinoic acid-induced gene I (RIG-I)-mediated RNA sensing and activation of the transcription factors IRF3 and IRF7 that drive IFN-I gene expression. Together, these findings suggest that m(6)A modifications of HIV-1 RNA evade innate immune sensing in myeloid cells.
 Microbiology Parasitology Virology Life Sciences & Biomedicine Science & Technology

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