A tail-like assembly at the portal vertex in intact herpes simplex type-1 virions

Herpes viruses are prevalent and well characterized human pathogens. Despite extensive study, much remains to be learned about the structure of the genome packaging and release machinery in the capsids of these large and complex double-stranded DNA viruses. However, such machinery is well characterized in tailed bacteriophage, which share a common evolutionary origin with herpesvirus. In tailed bacteriophage, the genome exits from the virus particle through a portal and is transferred into the host cell by a complex apparatus (i.e. the tail) located at the portal vertex. Here we use electron cryo-tomography of human herpes simplex type-1 (HSV-1) virions to reveal a previously unsuspected feature at the portal vertex, which extends across the HSV-1 tegument layer to form a connection between the capsid and the viral membrane. The location of this assembly suggests that it plays a role in genome release into the nucleus and is also important for virion architecture

A first update on mapping the human genetic architecture of COVID-19

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Visualization of a distinctive tegument structure associated with the portal vertex in HSV-1 virions.

<p>(<b>A</b>) Projection image through a tomogram of HSV-1 virions embedded in vitreous ice (<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002961#ppat.1002961.s002" target="_blank">Video S2</a>). (<b>B–C</b>) The symmetry-free virion averages generated from 213 subtomograms using MSA-guided classification and melon ball alignment methods, respectively. The maps are shown radially colored, with non-capsid densities trimmed to reveal the underlying capsid. Views are shown looking down a 2-fold axis of symmetry with the portal vertex at the bottom.</p

Comparison of portal and pentonal vertices.

<p>(<b>A</b>) Central section through an MSA-guided virion average. The left-hand panel shows a grey-scale density map. In the right-hand panel, the capsid shell is radially colored, with internal DNA density shown in cream, and portal density in purple. (<b>B–F</b>) Individual panels of the capsid shell cut away orthogonal to the axis running through the portal and opposing vertex, at the radii indicated by arrows in (<b>A</b>). Views are from the outside of the portal vertex (bottom) and its opposing pentonal vertex (top).</p

Workflow for MSA-guided classification.

<p>(<b>A</b>) Projected slices from a representative tomogram of HSV-1 virions. (<b>B</b>) 12 MSA-derived class averages, top, side and lower views. The class average representing a putative portal vertex is shown in yellow. (<b>C</b>) The putative portal vertex (top), the average of all other vertices (middle) and the difference map calculated from them (bottom), with the positive difference densities in blue, and negative difference density in red. (<b>D</b>) Final MSA-guided average, radially colored. (<b>E</b>) Flow chart of the procedure (described in detail within the <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002961#s4" target="_blank">Materials and Methods</a>).</p

Workflow for melon ball alignment.

<p>(<b>A</b>) Projected slices from a representative tomogram of HSV-1 virions. (<b>B</b>) 12 spherical masks (magenta), in an icosahedral arrangement, superimposed on a map of the capsid (grey), showing the relationship of the masks to the capsid surface. (<b>C</b>) Density extracted by the masking procedure in (<b>B</b>). After generating an initial model, the model may be updated iteratively by realigning the particles (red lines). (<b>D</b>) Final melon ball aligned average, radially colored. (<b>E</b>) Flow chart of the procedure (described in detail within the <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002961#s4" target="_blank">Materials and Methods</a>).</p

Visualizing red blood cell sickling and the effects of inhibition of sphingosine kinase 1 using soft X-ray tomography.

Sickle cell disease is a destructive genetic disorder characterized by the formation of fibrils of deoxygenated hemoglobin, leading to the red blood cell (RBC) morphology changes that underlie the clinical manifestations of this disease. Using cryogenic soft X-ray tomography (SXT), we characterized the morphology of sickled RBCs in terms of volume and the number of protrusions per cell. We were able to identify statistically a relationship between the number of protrusions and the volume of the cell, which is known to correlate to the severity of sickling. This structural polymorphism allows for the classification of the stages of the sickling process. Recent studies have shown that elevated sphingosine kinase 1 (Sphk1)-mediated sphingosine 1-phosphate production contributes to sickling. Here, we further demonstrate that compound 5C, an inhibitor of Sphk1, has anti-sickling properties. Additionally, the variation in cellular morphology upon treatment suggests that this drug acts to delay the sickling process. SXT is an effective tool that can be used to identify the morphology of the sickling process and assess the effectiveness of potential therapeutics