Abstract
SummaryHuman 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.
Highlights
We further show that viral DNA nucleates UL112-113 droplets, thereby ensuring that UL112-113 compartments form around genomes and establish a pro-replicative environment at a time of infection when overall UL112-113 concentrations are still low
Our results indicate that phase separation is essential for the structural integrity of pre-replication compartments (PRCs) and viral DNA replication
PRCs are fluid biomolecular condensates formed by liquid-liquid phase separation (LLPS) Pleomorphic Human cytomegalovirus (HCMV) nuclear replication compartments (RCs) arise from droplet-like PRCs (Ahn et al, 1999; Iwayama et al, 1994; Penfold and Mocarski, 1997) that phenotypically resemble fluid biomolecular condensates formed by LLPS (Brangwynne et al, 2009; Hyman et al, 2014; McSwiggen et al, 2019a)
Summary
Compartmentalization is a key feature of all living entities. A common separation mechanism in cell biology is cellular membranes that divide cells into distinct compartments. Eukaryotic cells harbor membrane-less compartments, such as Pbodies and stress granules in the cytosol and nucleoli, nuclear speckles, and Cajal bodies in the nucleus (Brangwynne et al, 2009; Fei et al, 2017; Feric et al, 2016; Fox et al, 2018; Strom and Brangwynne, 2019), which are commonly referred to as biomolecular condensates (Banani et al, 2017) Some of these compartments have liquid properties as reflected by their round shape and their ability to fuse and relax into larger spherical structures as a result of their surface tension as well as rapid diffusion of molecules within the body (Brangwynne et al, 2009; Hyman et al, 2014; McSwiggen et al, 2019a; Patel et al, 2015). It plays a role in buffering substrate concentrations to facilitate and promote biological reactions
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call