Human DDX3 Interacts with the HIV-1 Tat Protein to Facilitate Viral mRNA Translation

Abstract

Nuclear export and translation of intron-containing viral mRNAs are required for HIV-1 gene expression and replication. In this report, we provide evidence to show that DDX3 regulates the translation of HIV-1 mRNAs. We found that knockdown of DDX3 expression effectively inhibited HIV-1 production. Translation of HIV-1 early regulatory proteins, Tat and rev, was impaired in DDX3-depleted cells. All HIV-1 transcripts share a highly structured 5’ untranslated region (UTR) with inhibitory elements on translation of viral mRNAs, yet DDX3 promoted translation of reporter mRNAs containing the HIV-1 5’ UTR, especially with the transactivation response (TAR) hairpin. Interestingly, DDX3 directly interacts with HIV-1 Tat, a well-characterized transcriptional activator bound to the TAR hairpin. HIV-1 Tat is partially targeted to cytoplasmic stress granules upon DDX3 overexpression or cell stress conditions, suggesting a potential role of Tat/DDX3 complex in translation. We further demonstrated that HIV-1 Tat remains associated with translating mRNAs and facilitates translation of mRNAs containing the HIV-1 5’ UTR. Taken together, these findings indicate that DDX3 is recruited to the TAR hairpin by interaction with viral Tat to facilitate HIV-1 mRNA translation.

Venezuelan equine encephalitis virus non-structural protein 3 (nsP3) interacts with RNA helicases DDX1 and DDX3 in infected cells

“…Viruses such as HIV-1 (Edgcomb et al, 2012;Lai et al, 2013;Yasuda-Inoue et al, 2013) and HCV (Ariumi et al, 2007;Owsianka and Patel, 1999;Tingting et al, 2006) utilize both DDX1 and DDX3 to facilitate viral replication; likewise, in our studies, VEEV-nsP3 interacted with both DDX1 and DDX3. This opens the possibility that RNA helicases may serve compensatory roles in the viral life cycle.…”

“…DDX3 was observed to localize in SGs (Ariumi, 2014;Lai et al, 2013), where it associates with eIF4A, eIF4G, eIF2a, eIF3 and PABP to facilitate translation of mRNA containing structured 5 0 UTR (Ariumi, 2014;Lai et al, 2013;Shih et al, 2012). Of note, in our MS analysis, we also identified PABP as interacting with nsP3; however PABP fell below our condition of 50% reproducibility and therefore excluded from Fig.…”

“…There appears to be differential requirements of DEAD box proteins DDX1 and DDX3 by different viruses as evidenced by the observations with HIV-1, influenza, and now VEEV. In the case of HIV-1, DDX1 and DDX3 are critical co-factors that interact with HIV-1 Tat and Rev to promote HIV-1 mRNA translation and transition to late-stage HIV-1 infection (Lai et al, 2013). A recent study Fig.…”

“…For example, DDX1 facilitates replication of a number of viruses such as: Human immunodeficiency virus 1 (HIV-1) by interacting with HIV-1 Rev protein (Edgcomb et al, 2012); severe acute respiratory syndrome coronavirus, infectious bronchitis virus and mouse hepatitis virus (MHV) JHM strain (JHMV) through interactions with nsp14 (Xu et al, 2010) and phosphorylated nucleocapsid protein (Wu et al, 2014); and Hepatitis C virus (HCV) by binding to the 3 0 (þ) UTR and 5 0 (À) UTR (Tingting et al, 2006). Besides DDX1, DDX3, facilitates replication of Japanese encephalitis virus (JEV) through interactions with JEV NS3 and NS5 proteins, and the 5 0 and 3 0 UTR (Li et al, 2014); HIV-1 by interactions with HIV-1 Tat (Lai et al, 2013;Yasuda-Inoue et al, 2013) and HIV-1 Rev and cellular export receptor CRM1 (Lai et al, 2013); HCV by binding to the HCV core protein (Ariumi et al, 2007;Owsianka and Patel, 1999); and West Nile virus by binding to NS3 at viral replication sites (Chahar et al, 2013).…”

DDX3 Participates in Translational Control of Inflammation Induced by Infections and Injuries

“…Human DDX3 is a member of the DEAD box RNA helicase family, which are generally involved in ATP-dependent unwinding of doublestranded RNAs and remodeling of ribonucleoprotein complexes (1,2). DDX3 and its yeast homolog Ded1 have been implicated in various cellular processes (3), including transcription (4,5), precursor mRNA splicing (6)(7)(8), mRNA transport (9,10), and translation initiation (11)(12)(13)(14)(15)(16)(17)(18)(19). DDX3 has been reported to be primarily distributed throughout the cytoplasm in HeLa cells (15,17).…”