Herpes simplex virus 1 induces egress channels through marginalized host chromatin.

Markko Myllys,Carolyn A Larabell,Jussi Timonen,Vesa Aho,Visa Ruokolainen,Maija Vihinen-Ranta,Anna Salvetti,Veijo Hukkanen,Piritta Peri,Elizabeth A Smith,Satu Hakanen

doi:10.1038/srep28844

Abstract

Lytic infection with herpes simplex virus type 1 (HSV-1) induces profound modification of the cell nucleus including formation of a viral replication compartment and chromatin marginalization into the nuclear periphery. We used three-dimensional soft X-ray tomography, combined with cryogenic fluorescence, confocal and electron microscopy, to analyse the transformation of peripheral chromatin during HSV-1 infection. Our data showed an increased presence of low-density gaps in the marginalized chromatin at late infection. Advanced data analysis indicated the formation of virus-nucleocapsid-sized (or wider) channels extending through the compacted chromatin of the host. Importantly, confocal and electron microscopy analysis showed that these gaps frequently contained viral nucleocapsids. These results demonstrated that HSV-1 infection induces the formation of channels penetrating the compacted layer of cellular chromatin and allowing for the passage of progeny viruses to the nuclear envelope, their site of nuclear egress.

Highlights

Lytic infection with herpes simplex virus type 1 (HSV-1) induces profound modification of the cell nucleus including formation of a viral replication compartment and chromatin marginalization into the nuclear periphery
Transmission electron microscopy (TEM) and TEM tomography are limited by fixation-induced distortions of cellular features, damage caused by the electron beam and the limited range of angular sampling
Formation of a viral replication compartments (VRCs) as a result of herpes simplex virus type-1 (HSV-1) lytic infection is followed by structural changes in the host chromatin[5,37,38,39]

Summary

Introduction

Lytic infection with herpes simplex virus type 1 (HSV-1) induces profound modification of the cell nucleus including formation of a viral replication compartment and chromatin marginalization into the nuclear periphery. Confocal and electron microscopy analysis showed that these gaps frequently contained viral nucleocapsids These results demonstrated that HSV-1 infection induces the formation of channels penetrating the compacted layer of cellular chromatin and allowing for the passage of progeny viruses to the nuclear envelope, their site of nuclear egress. Each nucleocapsid penetrates the host chromatin layer and nuclear lamina to the inner nuclear envelope, the site of its egress[2,17,18] Despite their many achievements with biological applications, light- and electron-based imaging techniques suffer from fundamental limitations in 3D imaging of the subcellular architecture of the entire cell. Immunofluorescence imaging is prone to artefacts by fixation or permeabilization[19,20]

Methods

Results

Conclusion