HIV-1 Exploits a Dynamic Multi-aminoacyl-tRNA Synthetase Complex To Enhance Viral Replication

Abstract

A hallmark of retroviruses such as human immunodeficiency virus type 1 (HIV-1) is reverse transcription of genomic RNA to DNA, a process that is primed by cellular tRNAs. HIV-1 recruits human tRNA Lys3 to serve as the reverse transcription primer via an interaction between lysyl-tRNA synthetase (LysRS) and the HIV-1 Gag polyprotein. LysRS is normally sequestered in a multi-aminoacyltRNA synthetase complex (MSC). Previous studies demonstrated that components of the MSC can be mobilized in response to certain cellular stimuli, but how LysRS is redirected from the MSC to viral particles for packaging is unknown. Here, we show that upon HIV-1 infection, a free pool of non-MSC-associated LysRS is observed and partially relocalized to the nucleus. Heat inactivation of HIV-1 blocks nuclear localization of LysRS, but treatment with a reverse transcriptase inhibitor does not, suggesting that the trigger for relocalization occurs prior to reverse transcription. A reduction in HIV-1 infection is observed upon treatment with an inhibitor to mitogen-activated protein kinase that prevents phosphorylation of LysRS on Ser207, release of LysRS from the MSC, and nuclear localization. A phosphomimetic mutant of LysRS (S207D) that lacked the capability to aminoacylate tRNA Lys3 localized to the nucleus, rescued HIV-1 infectivity, and was packaged into virions. In contrast, a phosphoablative mutant (S207A) remained cytosolic and maintained full aminoacylation activity but failed to rescue infectivity and was not packaged. These findings suggest that HIV-1 takes advantage of the dynamic nature of the MSC to redirect and coopt cellular translation factors to enhance viral replication.IMPORTANCE Human tRNA Lys3 , the primer for reverse transcription, and LysRS are essential host factors packaged into HIV-1 virions. Previous studies found that tRNA Lys3 packaging depends on interactions between LysRS and HIV-1 Gag; however, many details regarding the mechanism of tRNA Lys3 and LysRS packaging remain unknown. LysRS is normally sequestered in a high-molecular-weight multi-aminoacyl-tRNA synthetase complex (MSC), restricting the pool of free LysRS-tRNA Lys . Mounting evidence suggests that LysRS is released under a variety of stimuli to perform alternative functions within the cell. Here, we show that HIV-1 infection results in a free pool of LysRS that is relocalized to the nucleus of target cells. Blocking this pathway in HIV-1-producing cells resulted in less infectious progeny virions. Understanding the mechanism by which LysRS is recruited into the viral assembly pathway can be exploited for the development of specific and effective therapeutics targeting this nontranslational function.KEYWORDS lysyl-tRNA synthetase, human immunodeficiency virus, multisynthetase complex, nuclear localization, tRNA primer packaging

Roles of aminoacyl-tRNA synthetases in immune regulation and immune diseases

“…Strikingly, other ARSs were not detected in HIV-1, suggesting that KRS might be specifically incorporated into viral particles 89,93 . Recently, Duchon et al 94 observed that HIV-1 infection triggered the release of KRS from the MSC to form a free pool of KRS, which might be due to the specific phosphorylation of S207 in KRS ( Fig. 3a).…”

Aminoacyl-tRNA synthetases, therapeutic targets for infectious diseases

“…Another study suggested that HIV-1 uses host mitochondrial KRS during the packaging process [74]. Because KRS is normally associated with the MSC, HIV-1 could exploit the dynamic nature of the MSC to redirect and co-opt cellular translation factors [75]. Indeed, HIV-1 infection triggers release of KRS from the MSC, possibly through phosphorylation at Ser207 [75].…”

“…Because KRS is normally associated with the MSC, HIV-1 could exploit the dynamic nature of the MSC to redirect and co-opt cellular translation factors [75]. Indeed, HIV-1 infection triggers release of KRS from the MSC, possibly through phosphorylation at Ser207 [75]. This PTM is important for KRS packaging into virions and progeny virus infectivity [75].…”

“…Indeed, HIV-1 infection triggers release of KRS from the MSC, possibly through phosphorylation at Ser207 [75]. This PTM is important for KRS packaging into virions and progeny virus infectivity [75]. The free pool of KRS translocates to the nucleus in a phosphorylation-dependent manner, although the relevance of nuclear KRS for viral infectivity is not yet entirely clear [75].…”

Role of host tRNAs and aminoacyl-tRNA synthetases in retroviral replication

“…The MSC serves as a reservoir for ARSs with noncanonical functions, as well as facilitating tRNA channeling and translation (61). Interestingly, HIV-1 infection leads to an increased pool of non-MSC-associated ARSs (62).…”