The Role Of UHRF1 In Regulating HIV-1 Transcription And Latency And The Discovery Of Novel Latency Reversal Agents

Acquired immunodeficiency syndrome,known as AIDS,is one of the most serious infectious diseases caused by Human Immunodeficiency virus(HIV)infection and characterized by the destruction of immune system followed by a series of infection complications leading to extremely high mortality.Currently,Highly Active Antiretroviral Therapy as the primary treatment for AIDS has successfully transformed AIDS into a chronic and manageable disease and shed light on the cure of AIDS.Due to HIV latent reservoir persisted in patients which is transcriptionally silent and fails to express viral proteins and produces progeny viruses during HIV infection.This proportion of provirus raises the resistance to antiretroviral therapy and host immunity,and causes durably latent HIV infection,which becomes the major obstacle for HIV cure.Therefore,lifelong antiretroviral therapy is required,if interrupted,viremia will rapidly rebound.Currently,the mechanism underlying HIV latency is still elusive,it is extremely important to understand the molecular mechanisms involved in modulating HIV-1 latency and designing potent latency reversing-agents for eliminating the HIV latent reservoir.The establishment and reversal of HIV latency has been closely modulated by viral protein Tat.To uncover the molecular mechanism of regulating Tat expression would contribute to further decipher the mechanism of HIV latency.As a viral positive transcription factor,Tat is critical for the regulation of HIV transcription.In latent state,low expression of Tat facilitates to maintain the transcriptional silence of HIV.Once reversing to reactivation state,Tat promotes transcriptional extension by relieving the transcriptional inhibition of negative elongation factor and DRB sensitivity-inducing factor.Several studies have shown that the host regulates Tat expression through a variety of pathways,such as autophagy,lysosome and ubiquitinproteasome pathway,leading to insufficient Tat expression followed by the establishment of HIV latency.Recent studies show the function of Ubiquitin-like PHD and RING finger domain-containing protein 1(UHRF1)on the infection of HBV,EBV and influenza virus.As a multifunctional epigenetic effector,UHRF1 plays important roles in DNA and histone methylation,protein ubiquitination,which is closely related to HIV replication and latency.It is worthy of exploring the role of UHRF1 involved in HIV-1 replication and the maintenance of latent reservoir.This study aims to explore the function of UHRF1 in HIV-1 replication and latency,and decipher the underlying molecular mechanisms,which may facilitate to develop novel HIV-1 latent reversal agents targeting UHRF1.Here,we showed that UHRF1 negatively modulates HIV-1 transcription by binding to 5’ long terminal repeat(LTR)of viral genome via ChIP assay.Furthermore,we found UHRF1 depletion significantly promoted transcriptional initiation and extension of HIV-1,suggesting that UHRF1,as a novel HIV-1 restriction factor,may modulate HIV latency.In HIV latent model,UHRF1 depletion reversed the latency of HIV-1 proviruses and synergistically promoted the reactivation with classical latent infection reversal agents.Mechanistically,UHRF1 competed with positive transcription factor b(p-TEFb)for the binding to the cysteine-rich motifs of HIV-1 Tat via its TTD,PHD,and RING finger domains.Furthermore,UHRF1 mediated K48-linked ubiquitination and proteasomal degradation of Tat in RING-dependent ways,leading to the impediment of transcription elongation and consequential HIV-1 latency.Further studies found that the treatment of small molecule compound Q205 significantly reduced the expression of UHRF1 and promoted HIV-1 latent reactivation,indicating the role of Q205 as a latent reversal agent by inhibiting UHRF1.In summary,for the first time,our findings revealed the regulatory function of UHRF1 in HIV-1 latency and underlying molecular mechanisms with HIV-1 latent model,providing novel insights on host-pathogen interaction for modulating HIV-1 latency,and important theoretical basis and novel drug targets for the development of HIV-1 latent reversal agents.