HIV latency reversing agents act through Tat post translational modifications

Abstract

BackgroundDifferent classes of latency reversing agents (LRAs) are being evaluated to measure their effects in reactivating HIV replication from latently infected cells. A limited number of studies have demonstrated additive effects of LRAs with the viral protein Tat in initiating transcription, but less is known about how LRAs interact with Tat, particularly through basic residues that may be post-translationally modified to alter the behaviour of Tat for processive transcription and co-transcriptional RNA processing.ResultsHere we show that various lysine and arginine mutations reduce the capacity of Tat to induce both transcription and mRNA splicing. The lysine 28 and lysine 50 residues of Tat, or the acetylation and methylation modifications of these basic amino acids, were essential for Tat transcriptional control, and also for the proviral expression effects elicited by histone deacetylase inhibitors (HDACi) or the bromodomain inhibitor JQ1. We also found that JQ1 was the only LRA tested that could induce HIV mRNA splicing in the absence of Tat, or rescue splicing for Tat lysine mutants in a BRD4-dependent manner.ConclusionsOur data provide evidence that Tat activities in both co-transcriptional RNA processing together with transcriptional initiation and processivity are crucial during reactivation of latent HIV infection. The HDACi and JQ1 LRAs act with Tat to increase transcription, but JQ1 also enables post-transcriptional mRNA splicing. Tat residues K28 and K50, or their modifications through acetylation or methylation, are critical for LRAs that function in conjunction with Tat.Electronic supplementary materialThe online version of this article (10.1186/s12977-018-0421-6) contains supplementary material, which is available to authorized users.

Integrated Assessment of Viral Transcription, Antigen Presentation, and CD8+T Cell Function Reveals Multiple Limitations of Class I-Selective Histone Deacetylase Inhibitors during HIV-1 Latency Reversal

“…MS RNAs encode the regulatory proteins Tat, Rev, and Nef, which are required for successful viral replication. Tat is particularly important in driving robust viral transcription and elongation and coordinating viral splicing (71), and the absence of Tat is more essential than the cellular environment in maintaining viral latency (72). Unspliced transcripts contain secondary structures termed the Rev response element (RRE), which retain HIV-1 RNAs in the nucleus.…”

“…Alternatively, should Tat become expressed during latency reversal, long noncoding RNAs present in mCD4 ϩ T cells may selectively promote the degradation of Tat protein (78). Tat posttranslational modifications driven by the acetylation of lysine residues by HDACi may additionally alter the behavior of Tat in its replication feedback loop, also affecting the ability to form virions (71). The capacity to reverse latency will also depend on the environment of the host cell.…”

Harnessing host–virus evolution in antiviral therapy and immunotherapy

“…HAT and HDAC inhibitors have been shown to suppress viral transcription (‘kill’) and re‐activate latent virus (‘shock‐and‐kill’), respectively, suggesting epigenetic remodulation of host gene activity is exceptionally important in the replication strategy of HIV‐1 and other retroviruses. Alternatively, retroviral proteins may block or usurp the enzymatic activity of HAT p300 to direct acetylation of viral or other host proteins, which has been suggested for Tat . The interactions between HAT p300 and HIV‐1 proteins Tat, Vpr and Pol (Figure ), together with the large number of HAT p300 inhibitors currently available (Table ), expand the possibilities for targeting HAT p300 in host‐oriented antiretroviral therapies.…”

Role of Divalent Cations in HIV-1 Replication and Pathogenicity

“…When Tat-TAR interaction problems occur, HIV-1 transcription prematurely terminates and HIV-1 can reside inside cells in the latent phase [91,92]. However, HIV-1 can exhibit latency breakthrough resulting from modulation of Tat and TAR interactions by stimulatory factors generally [93,94] and specifically by divalent cations [95,96].…”