HIV-1 chromatin, transcription, and the regulatory protein Tat

Human chromatin remodelers regulating HIV-1 transcription: a target for small molecule inhibitors

HIV-1 can establish a lifelong infection by incorporating its proviral DNA into the host genome. Once integrated, the virus can either remain dormant or start active transcription, a process governed by the HIV Tat protein, host transcription factors and the chromatin landscape at the integration site. Histone-modifying enzymes and chromatin-remodeling enzymes play crucial roles in regulating this chromatin environment. Chromatin remodelers, a group of ATP-dependent proteins, collaborate with host proteins and histone-modifying enzymes to restructure nucleosomes, facilitating DNA repair, replication, and transcription. Recent studies have highlighted the importance of chromatin remodelers in HIV-1 latency, spurring research focused on developing small molecule modulators that can either reactivate the virus for eradication approaches or induce long-term latency to prevent future reactivation. Research efforts have primarily centered on the SWI/SNF family, though much remains to be uncovered regarding other chromatin remodeling families. This review delves into the general functions and roles of each chromatin remodeling family in the context of HIV and discusses recent advances in small molecule development targeting chromatin remodelers and the HIV Tat protein, aiming to improve therapeutic approaches against HIV.

Depicting HIV-1 Transcriptional Mechanisms: A Summary of What We Know

Despite the introduction of combinatory antiretroviral therapy (cART), HIV-1 infection cannot be cured and is still one of the major health issues worldwide. Indeed, as soon as cART is interrupted, a rapid rebound of viremia is observed. The establishment of viral latency and the persistence of the virus in cellular reservoirs constitute the main barrier to HIV eradication. For this reason, new therapeutic approaches have emerged to purge or restrain the HIV-1 reservoirs in order to cure infected patients. However, the viral latency is a multifactorial process that depends on various cellular mechanisms. Since these new therapies mainly target viral transcription, their development requires a detailed and precise understanding of the regulatory mechanism underlying HIV-1 transcription. In this review, we discuss the complex molecular transcriptional network regulating HIV-1 gene expression by focusing on the involvement of host cell factors that could be used as potential drug targets to design new therapeutic strategies and, to a larger extent, to reach an HIV-1 functional cure.

Phosphorylation Targets of DNA-PK and Their Role in HIV-1 Replication

The DNA dependent protein kinase (DNA-PK) is a trimeric nuclear complex consisting of a large protein kinase and the Ku heterodimer. The kinase activity of DNA-PK is required for efficient repair of DNA double-strand breaks (DSB) by non-homologous end joining (NHEJ). We also showed that the kinase activity of DNA-PK is essential for post-integrational DNA repair in the case of HIV-1 infection. Besides, DNA-PK is known to participate in such cellular processes as protection of mammalian telomeres, transcription, and some others where the need for its phosphorylating activity is not clearly elucidated. We carried out a systematic search and analysis of DNA-PK targets described in the literature and identified 67 unique DNA-PK targets phosphorylated in response to various in vitro and/or in vivo stimuli. A functional enrichment analysis of DNA-PK targets and determination of protein-protein associations among them were performed. For 27 proteins from these 67 DNA-PK targets, their participation in the HIV-1 life cycle was demonstrated. This information may be useful for studying the functioning of DNA-PK in various cellular processes, as well as in various stages of HIV-1 replication.

The role of enhancer of zeste homolog 2: From viral epigenetics to the carcinogenesis of hepatocellular carcinoma

Nowadays, epigenetics covers a crucial role in different fields of science. The enhancer of zeste homolog 2 (EZH2), the catalytic subunit of the Polycomb Repressive Complex 2 (PRC2), is a big proponent of how epigenetic changes can affect the initiation and progression of several diseases. Through its catalytic activity, responsible for the tri-methylation of lysine 27 of the histone H3 (H3K27me3), EZH2 is a good target for both diagnosis and therapy of different pathologies. A large number of studies have demonstrated its crucial role in cancer initiation and progression. Nevertheless, only recently its function in virus diseases has been uncovered; therefore, EZH2 can be an important promoter of viral carcinogenesis. This review explores the role of EZH2 in viral epigenetics based on recent progress that demonstrated the role of this protein in virus environment. In particular, the review focuses on EZH2 behavior in Hepatitis B Virus, analyzing its role in the rise of Hepatocellular Carcinoma.

RNA glycosidase and other agents target Tat to inhibit HIV-1 transcription

The HIV-1 tat gene encodes a small 86-104 amino acid protein depending on the HIV-1 strain. Tat is essential for HIV-1 replication through interactions with numerous cellular transcription factors. The interaction between Tat and P-TEFb, which is a cellular protein complex composed of cyclin T1 and CDK9, delivers P-TEFb to the newly transcribed viral mRNAs where phosphorylation of RNA polymerase II by CDK9 leads to highly efficient mRNA transcription. It has long been recognized that Tat is a potential anti-HIV-1 target and possibly a viral Achilles' heel. However, specifically targeting Tat without affecting normal host cell functions has been challenging. Means to inactivate Tat have been reported that includes small compounds, transdominant negative Tat proteins, and by plant-derived antivirals. Investigations of these agents have reported encouraging outcomes that inform and may hopefully affect strategies for a functional HIV-1 cure.

Unravelling HIV-1 Latency, One Cell at a Time

A single virus is capable of infecting and replicating in a single cell. Recent advances across single-cell omics technologies - genomics, epigenomics, transcriptomics, epitranscriptomics, proteomics, and metabolomics - will offer unprecedented opportunities to gain more insights into the various aspects of the life cycle of viruses and their impact on the host cell. Here, using the human immunodeficiency virus type 1 (HIV-1) as an example, we summarize the current knowledge and the future potential of single-cell omics in the investigation of an important aspect of the life cycle of HIV-1 that represents a major hurdle in achieving viral eradication, HIV-1 latency.