Project Details
Projekt
Integrative characterisation of viral and cellular regulation of human cytomegalovirus replication
Applicant
Professor Dr. Jens Bernhard Bosse
Subject Area
Virology
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 443644894
Human cytomegalovirus (HCMV) is a major opportunistic pathogen that threatens immunocompromised individuals and is a leading cause of congenital infection. Its intricate replication cycle is governed by the competition of viral and cellular factors at viral genomes. Our recent findings show that the HCMV UL112-113 proteins assemble dynamic, phase-separated prereplication compartments (PRCs) at viral genomes early in infection. As infection progresses, these fluid PRCs transition into gel-like replication compartments that orchestrate viral DNA synthesis. Our biochemical and structural data indicate that the conserved N-terminal domain of UL112-113 oligomerizes into fiber-like assemblies, which we hypothesize function as a viral nucleoprotein scaffold. Consistent with this hypothesis, two small-molecule inhibitors we identified disrupt UL112-113 fiber formation in vitro and block viral replication, suggesting that fiber assembly is critical for HCMV propagation. On the host side, promyelocytic leukemia (PML) nuclear bodies (PML-NBs) constitute an important antiviral defense. These membrane-less organelles incorporate multiple PML isoforms, but the roles of individual isoforms in HCMV infection are not fully understood. Our structural predictions and preliminary biochemical analyses point to the unique, C-terminal exonuclease-like (Exo) domain of PML-I as an RNA-binding module that may recognize transcribing viral genomes. We hypothesize that PML-I Exo-mediated detection helps recruit or stabilize antiviral effectors at viral DNA, creating a repressive chromatin state. In turn, we propose that UL112-113 fibers compete with PML-NBs by coating and structurally reorganizing the viral genome, thereby limiting PML-mediated restriction and establishing a replication-favorable environment. This proposal will define the molecular function of the PML-I Exo domain, determine how it binds viral RNA, and clarify whether its exonuclease-like or RNA-binding activity triggers a broader antiviral response. Concomitantly, we will elucidate the mechanism of UL112-113 fiber formation and investigate how these fibers emerge from initial fluid condensates at the viral genome, facilitate replication compartment maturation, and recruit essential viral factors. By combining structural biology, advanced imaging, and functional virology in an integrative approach, we aim to resolve how these two membrane-less structures - PML-NBs and UL112-113 assemblies - converge at the viral genome and act as a critical regulatory checkpoint.
DFG Programme
Research Units
