Human cytomegalovirus forms phase-separated compartments at viral genomes to facilitate viral replication

• Published in: Cell reports (Cambridge) 2022-03, Vol.38 (10), p.110469, Article 110469
• Main Authors: Caragliano, Enrico, Bonazza, Stefano, Frascaroli, Giada, Tang, Jiajia, Soh, Timothy K., Grünewald, Kay, Bosse, Jens B., Brune, Wolfram
• Format: Article
• Language: English
• Subjects: Cell Nucleus - metabolism; Cytomegalovirus - genetics; Cytomegalovirus - metabolism; DNA, Viral - genetics; DNA, Viral - metabolism; Genome, Viral; Herpesviridae; human cytomegalovirus; human herpesvirus 5; Humans; liquid-liquid phase separation; live-cell imaging; LLPS; membrane-less organelle; molecular virology; phase transition; replication compartment; Viral Proteins - metabolism; viral replication; Virus Replication
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2022.110469

Human cytomegalovirus (HCMV) replicates its DNA genome in specialized replication compartments (RCs) in the host cell nucleus. These membrane-less organelles originate as spherical structures and grow in size over time. However, the mechanism of RC biogenesis has remained understudied. Using live-cell imaging and photo-oligomerization, we show that a central component of RCs, the UL112-113 proteins, undergo liquid-liquid phase separation (LLPS) to form RCs in the nucleus. We show that the self-interacting domain and large intrinsically disordered regions of UL112-113 are required for LLPS. Importantly, viral DNA induces local clustering of these proteins and lowers the threshold for phase separation. The formation of phase-separated compartments around viral genomes is necessary to recruit the viral DNA polymerase for viral genome replication. Thus, HCMV uses its UL112-113 proteins to generate RCs around viral genomes by LLPS to ensure the formation of a pro-replicative environment. [Display omitted] •HCMV pre-replication compartments are fluid biomolecular condensates•The viral UL112-113 proteins mediate LLPS•Incoming viral genomes nucleate phase separation•Phase separation facilitates recruitment of replication factors Human cytomegalovirus replicates its DNA genome in specialized replication compartments in the host cell nucleus. Caragliano et al. show how the viral UL112-113 proteins undergo liquid-liquid phase separation at viral genomes to form replication compartments and how phase separation promotes the recruitment of the viral DNA polymerase.