Wallet, C. | Search bioRxiv

bioRxiv2026

THE HIV-1 SILENCER BCL11B/CTIP2 REGULATES THE TLR3-MEDIATED CELLULAR RESPONSE TO VIRAL INFECTIONS

HIV-1 latency remains a major barrier to viral eradication. The persistence of the latently infected reservoirs results from multifactorial mechanisms controlling gene transcription and cellular responses to viral reactivation. The transcriptional repressor BCL11B/CTIP2 is known to promote the establishment and persistence of the latently infected reservoirs. However, its contribution to the cellular response to viral infection has not been investigated before. Together with HEXIM1, paraspeckles contribute to cellular innate sensing of viral infections and to the production of type I interferons. Paraspeckles are nuclear membrane-less organelles composed of proteins, including SFPQ/PSF and NONO, wrapped around the long non-coding RNA NEAT1. Here, we show that HIV-1 infection promotes a TLR3-mediated CTIP2 overexpression delayed from a transitory NEAT1 overexpression, paraspeckles formation and type I IFN production. In response to this interferon production, CTIP2 is recruited to the NEAT1 promotor together with HEXIM1 and repressive histone marks to inhibit NEAT1 gene expression. The resulting depletion of the paraspeckles abrogated INF production, dampening TLR3 signalling and reinforcing HIV-1 latency. Our results demonstrate CTIP2 as a dual-function regulator that silences HIV-1 transcription and restricts antiviral innate immune response as part of a negative feedback loop limiting the interferon response to viral infection. O_FIG O_LINKSMALLFIG WIDTH=147 HEIGHT=200 SRC="FIGDIR/small/699245v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@7ab0b0org.highwire.dtl.DTLVardef@e60aa6org.highwire.dtl.DTLVardef@c5564corg.highwire.dtl.DTLVardef@1a4bbe0_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2020

Inhibition of HIV-1 gene transcription by KAP1 in myeloid lineage

HIV-1 latency generates reservoirs that prevent viral eradication by the current therapies. To find strategies toward an HIV cure, detailed understandings of the molecular mechanisms underlying establishment and persistence of the reservoirs are needed. The cellular transcription factor KAP1 is known as a potent repressor of gene transcription. Here we report that KAP1 represses HIV-1 gene expression in myeloid cells including microglial cells, the major reservoir of the central nervous system. Mechanistically, KAP1 interacts and colocalizes with the viral transactivator Tat to promote its degradation via the proteasome pathway and repress HIV-1 gene expression. In myeloid models of latent HIV-1 infection, the depletion of KAP1 increased viral gene elongation and reactivated HIV-1 expression. Bound to the latent HIV-1 promoter, KAP1 associates and cooperates with CTIP2, a key epigenetic silencer of HIV-1 expression in microglial cells. In addition, Tat and CTIP2 compete for KAP1 binding suggesting a dynamic modulation of the KAP1 cellular partners upon HIV-1 infection. Altogether, our results suggest that KAP1 contributes to the establishment and the persistence of HIV-1 latency in myeloid cells.

molecular biology↗