Work

Majority of the latent reservoir resides in CD32a negative CD4+ T cells

Year: 2017

Type: article

Abstract: Background: During latency HIV-1 expression is restricted via epigenetic events including histone methylation that position nucleosomes Nuc-0 and Nuc-1 at the 5'LTR.Enhancer of zeste homolog 2 (EZH2) is a member of the polycomb repressor complex 2 (PRC2) and the dominant histone methyltransferase that suppresses HIV-1 5'LTR activity via trimethylation of lysine 27 on histone H3 (H3K27me3).In higher eukaryotic cells, PRC2 is recruited to the chromain by long noncoding RNAs molecules (lncRNA).How are Nuc-0 and Nuc-1 precisely and invariably positioned at the 5'LTR irrespective of the integration site and orientation?What is the lncRNA that recruits PCR2 to the 5'LTR?An hypothesis is that HIV-1 encodes for its own lncRNA that recruits PRC2 to the 5'LTR, thus establishing latency regardless of the surrounding chromatin.HIV-1 expresses an antisense transcript (Ast) from a promoter located within the 3'LTR.Methods: We generated cell lines stably transduced with a lentivirus expressing Ast, and we studied its effect on viral replication, on the establishment and maintenance of latency, and on epigenetic regulation of HIV-1 transcription.Results: We found that Ast is expressed in many infected cell types, including chronically infected cell lines, primary CD4+ T cells infected in vitro, as well as resting memory CD4+ T cells from HIV-1 infected individuals under cART.HIV-1 infection of Jurkat cells stably transduced with a lentivirus expressing Ast results in reduced viral replication.Reactivation of HIV-1 in latently infected Jurkat E4 cells stably transduced with the same lentiviral construct (JE4AST) is significantly reduced, whereas return to latency is accelerated.ChIP assays showed that RNA Pol II is nearly absent at the HIV-1 promoter in JE4AST cells, and that its presence does not increase following stimulation with LRA.On the other hand, EZH2 and H3K27me3 persist at high levels at Nuc-1 in JE4AST cells even after exposure to LRA.Finally, we demonstrate that Ast associates with PRC2.Conclusions: Altogether, these results show that Ast is an HIVencoded inducer of viral latency that recruits PRC2 to the 5'LTR, leading to nucleosome assembly and chromatin silencing.Ast could be used to design new therapeutic agents for durable HIV-1 silencing and latency stabilization.

Source: Journal of Virus Eradication

DOI: 10.1016/s2055-6640(20)30527-6