Structural basis of human cytomegalovirus replication within host cells

University Of California Los Angeles, Los Angeles CA

Investigators

Linked publications, trials & patents

Abstract

PROJECT SUMMARY/ABSTRACT Human cytomegalovirus (HCMV) is a ubiquitous human herpesvirus found in up to 90% of adults. Active HCMV infection (often referred to simply as CMV by clinicians) can manifest as chronic oral ulcerations and sialadenitis, and is a major viral cause of birth defects and life-threatening conditions in immunosuppressed individuals. HCMV is largely innocuous in healthy adults, but for newborns and the immune-compromised, such as those with AIDS or organ transplant recipients, the dearth of effective HCMV therapies or vaccines poses a grave risk. HCMV, a member of the β-herpesvirus subfamily of the Herpesviridae, is the most structurally and genetically complex herpesvirus (e.g., its genome is twice that of chickenpox-causing varicella zoster virus, an α-herpesvirus). Architecturally similar to other herpesviruses, HCMV virion consists of four concentric, largely pleomorphic layers: a glycoprotein-decorated envelope, a large, ill-defined tegument layer, and a bacteriophage-like icosahedral capsid enclosing a dsDNA genome of 230,000 base pairs. In the current funding cycle, the PI’s group published the cryogenic electron microscopy (cryoEM) and tomography (cryoET) structures of these layers of HCMV and related β-herpesviruses (human herpesvirus 6 and murine cytomegalovirus) in a series of high-impact papers and discovered two live-attenuated mutants through structure-guided mutagenesis with co-I Tang lab (vaccine patent pending). Among them are the first in situ structures of gB and gB-gH/gL complexes on the HCMV envelope, the atomic structures of the genome- translocating portal complex, capsid-associated tegument proteins of HCMV and other herpesviruses, as well as human tRNA bound to the HCMV-specific tegument phosphoprotein, pp150. The renewal application builds on these successes and harness the PI’s machine learning-empowered cryoEM and cryoET technologies, and the co-I’s complementary virology expertise, to determine the native structures of the so-far poorly defined phosphorylated tegument proteins and tRNA interaction in HCMV and to explore their potential roles in CMV infections. Our central hypothes is that HCMV packages a myriad of molecules—including human tRNA and switchable phosphoproteins—and release them to modulate immune systems and promote replication within host cells. First, we will define cell-line specific recruitment of human tRNA by the CMV-specific tegument protein pp150 and explore the roles of virion-containing human tRNA in replication (Aim 1). Second, we will obtain native atomic structures of pp65, pp71 and by structure-guided mutagenesis, elucidate critical interactions within the HCMV tegument, focusing on the phosphoproteins pp150, pp65, and pp71 (Aim 2). Finally, by AI-empowered cellular cryoET, we will define how uncoated HCMV particles with inner tegument proteins undergo microtubule-guided retrograde transport and dock at nuclear pore complexes to facilitate genome ejection into the nucleus (Aim 3). The expected results will elucidate the mechanisms of tegument protein-host interactions governing viral replication and inform efforts to develop anti-HCMV therapies.