The HCMV Assembly Compartment Is a Dynamic Golgi-Derived MTOC that Controls Nuclear Rotation and Virus Spread

Abstract

Human cytomegalovirus (HCMV), a leading cause of congenital birth defects, forms an unusual cytoplasmic virion maturation site termed the "assembly compartment" (AC). Here, we show that the AC also acts as a microtubule-organizing center (MTOC) wherein centrosome activity is suppressed and Golgi-based microtubule (MT) nucleation is enhanced. This involved viral manipulation of discrete functions of MT plus-end-binding (EB) proteins. In particular, EB3, but not EB1 or EB2, was recruited to the AC and was required to nucleate MTs that were rapidly acetylated. EB3-regulated acetylated MTs were necessary for nuclear rotation prior to cell migration, maintenance of AC structure, and optimal virus replication. Independently, a myristoylated peptide that blocked EB3-mediated enrichment of MT regulatory proteins at Golgi regions of the AC also suppressed acetylated MT formation, nuclear rotation, and infection. Thus, HCMV offers new insights into the regulation and functions of Golgi-derived MTs and the therapeutic potential of targeting EB3.

RACK1 evolved species-specific multifunctionality in translational control through sequence plasticity in a loop domain

“…After washing, detection was performed using Pierce ECL western blot substrate (Thermo Fisher) followed by exposure to X-ray film. Western blots were quantified using densitometry as described previously (Procter et al, 2018).…”

Golgi Structure and Function in Health, Stress, and Diseases

“…As a highly dynamic organelle, Golgi serves as a membrane scaffold for multiple viruses, including infectious hepatitis C virus, enteroviruses, poliovirus, foot-and-mouth-disease virus, dengue virus, coronavirus, Kunjin virus, tick-borne encephalitis virus, rubella virus, and bunyamwera virus (Miller and Krijnse-Locker 2008;Harak and Lohmann 2015;Risco et al 2003;Salanueva et al 2003;Delgui et al 2013;Westerbeck and Machamer 2015), and is frequently fragmented after infection (Campadelli et al 1993;Salanueva et al 2003;Yadav et al 2016;Avitabile et al 1995;Lavi et al 1996;Hansen et al 2017;Rebmann et al 2016). Viruses use Golgi membranes directly and/or hijack master controllers of Golgi biogenesis and trafficking to generate vesicles that are used as the site of viral RNA replication (Quiner and Jackson 2010;Hansen et al 2017;Short et al 2013), wrapping (Sivan et al 2016;Alzhanova and Hruby 2007;Alzhanova and Hruby 2006;Nanbo et al 2018;Lundu et al 2018;Procter et al 2018), intracellular transduction (Nonnenmacher et al 2015), and secretion ). Viral infection triggers Golgi fragmentation via diverse mechanisms, ranging from phosphorylating key Golgi structural proteins such as GRASP65 (Rebmann et al 2016), activating the Src kinase to phosphorylate the Dynamin 2 GTPase (Martin et al 2017), targeting the immunity-related GTPase M (IRGM) to the Golgi to induce GBF1 phosphorylation (Hansen et al 2017), modulating vesicular trafficking (Yadav et al 2016;Johns et al 2014), to impeding the major histocompatibility complex (MHC) class I trafficking, antigen presentation, and/or cytokine secretion Rohde et al 2012).…”

HCMV Assembly Is Totally Tubular

“…Virologists often think of microtubules in terms of viral entry, and cell biologists largely think about their formation in terms of centrosomes. The work presented here by Procter et al (2018) will help each group to reconsider their long-held impressions of microtubule function and regulation. Furthermore, the authors demonstrate how live-cell imaging of viral infections is particularly amenable to the study of rare or complex cellular events.…”

“…Over the hours, decades, and millennia, HCMV has learned a lot of cell biology during these infections. In this issue of Developmental Cell, Procter et al (2018) report some of that knowledge that they have pried loose by using live-cell imaging to watch, in real time, how HCMV alters cellular architecture to facilitate its own assembly. The authors observed nuclear somersaults and Golgi-derived structures splitting and fusing.…”

“…But HCMV inactivates centrosomes (Hertel and Mocarski, 2004), making the HCMVinfected cell the perfect place to study the cell biology of Golgi-derived microtubules and their roles in viral egress. Procter et al (2018) began with a simple question: what does the assembly compartment look like over the course of a viral life cycle? However, before they could even think about the AC, they were amazed (and you will be, too) to see the infected cell nuclei spin like a top, with the majority of nuclei rotating more than 180 on their axis.…”