Biology subjects

Bloor, S.

Publications and source records attributed to Bloor, S..

4 recordsLinked to original sources

bioRxiv2024

An essential role for RNA binding by Periphilin in silencing by the HUSH complex

The human silencing hub (HUSH) complex is a transcription-dependent, epigenetic repressor complex that provides a genome-wide immunosurveillance system for the recognition and silencing of newly-integrated retroelements. The core HUSH complex of TASOR, MPP8 and Periphilin, represses these retroelements through SETDB1-mediated H3K9me3 deposition and MORC2-dependent chromatin compaction. HUSH-dependent silencing is RNA-mediated, yet no HUSH components contain any RNA-binding domain. Here we used an unbiased approach to identify which HUSH component was able to bind RNA and determine whether RNA-binding was essential for HUSH function. We identify Periphilin as the major RNA-binding component of the HUSH complex and show that Periphilins N-terminal domain is essential for both RNA binding and HUSH function. Periphilin binding to RNA was independent of its interaction with TASOR or MPP8, as its N-terminal domain was sufficient for RNA targeting. The artificial tethering of Periphilin to a HUSH-insensitive, nascent transcript, enabled the HUSH-dependent silencing of the transcript. This tethering of Periphilin allowed the RNA-binding region of Periphilin to be removed such that only its C-terminal domain was required for oligomerisation and interaction with TASOR. We therefore show that Periphilin is the predominant RNA-binding protein of the HUSH complex and this RNA-binding is essential for HUSH activity.

genetics↗

bioRxiv2024

The HUSH epigenetic repressor complex silences PML nuclear bodies-associated HSV-1 quiescent genomes

Herpes simplex virus 1 (HSV-1) latently infected neurons show multiple patterns in the distribution of the viral genomes within the nucleus, at least in mouse models. One of the major patterns is characterized by the presence of quiescent HSV-1 genomes trapped in promyelocytic leukemia nuclear bodies (PML NBs) to form viral DNA-containing PML-NBs (vDCP NBs). Using a cellular model reproducing the formation of vDCP NBs we previously showed that viral genomes are chromatinized with the H3.3 histone variant modified on its lysine 9 by tri-methylation (H3.3K9me3) a chromatin mark associated with transcriptional repression. Here we identify an essential role for the HUSH complex and its SETDB1 and MORC2 effectors in the acquisition of the H3K9me3 mark on the PML NBs-associated HSV-1 and in the maintenance of HSV-1 transcriptional repression. ChiP-seq analyses highlight the association of the H3K9me3 mark with the entire viral genome. Inactivating the HUSH-SETDB1-MORC2 repressor complex prior to viral infection results in a significant reduction of H3K9me3 on the viral genome, while the overall impact on the cellular genome is minimal, except for expected changes in families of LINE1 retroelements. Depletion of HUSH, SETDB1, or MORC2, relieves the repressive state of HSV-1 in infected primary human fibroblasts as well as human induced pluripotent stem cell-derived sensory neurons (hiPSDN). We discovered that the viral protein ICP0 induces MORC2 degradation via the proteasome machinery. This process is concurrent with ICP0 and MORC2 depletion capability to reactivate silenced HSV-1 in hiPSDN. Overall, our findings underscore the robust antiviral function of the HUSH-SETDB1-MORC2 repressor complex against a herpesvirus by modulating chromatin marks linked to repression, thus presenting promising avenues for novel anti-herpesvirus therapeutic strategies. Significance statementHerpes simplex virus 1 (HSV-1) is a major human pathogen, which remains latent in the trigeminal ganglia (TG) neurons of the infected individuals. Its reactivation is characterized by a variety of clinical symptoms the most severe ones being keratitis and herpesvirus encephalitis. The colonization of the CNS by the virus during the individual life is a well-known fact but the pathophysiological effects on neurons homeostasis are still underestimated. It is thus paramount to understand the molecular mechanisms that control HSV-1 latency and maintain the virus in a pseudo silent state.

microbiology↗

bioRxiv2021

Human embryonic stem cell-derived cardiomyocytes express SARS-CoV-2 host entry proteins: screen to identify inhibitors of infection

Patients with cardiovascular comorbidities are more susceptible to severe infection with SARS-CoV-2, known to directly cause pathological damage to cardiovascular tissue. We outline a screening platform using human embryonic stem cell-derived cardiomyocytes, confirmed to express the protein machinery critical for SARS-CoV-2 infection, and a pseudotyped virus system. The method has allowed us to identify benztropine and DX600 as novel inhibitors of SARS-CoV-2 infection.

pharmacology and toxicology↗

bioRxiv2017

Neuropathic mutations in MORC2 perturb GHKL ATPase dimerization dynamics and epigenetic silencing by multiple structural mechanisms

Missense mutations in MORC2 cause neuropathies including spinal muscular atrophy and Charcot-Marie-Tooth disease. We recently identified MORC2 as an effector of epigenetic silencing by the HUSH complex. Here we report the biochemical and cellular activities of MORC2 variants, alongside crystal structures of wild-type and neuropathic forms of a human MORC2 fragment comprising the GHKL-type ATPase module and CW-type zinc finger. This fragment dimerizes upon binding ATP and contains a hinged, functionally critical coiled coil insertion absent in other GHKL ATPases. We find that dimerization and DNA binding of the MORC2 ATPase module transduce HUSH-dependent silencing. Disease mutations change the dynamics of dimerization by distinct structural mechanisms: destabilizing the ATPase-CW module, trapping the ATP lid or perturbing the dimer interface. These defects lead to modulation of HUSH function, thus providing a molecular basis for understanding MORC2-associated neuropathies.

biochemistry↗