Anastasia Gazi

Viruses were for quite long characterized as the invisible heteronomous agents, (unseen by light microscopy & unable to propagate themselves in the absence of susceptible cells) capable of escaping the bacteriological filters (Rivers, 1932, The nature of viruses).

It was the birth and rise of the Electron Microscope that finally revealed the true nature of viruses, giving an exponential boost to Virology: Viruses are indeed so small that enter the susceptible cells and hijack their cellular machineries to replicate their genomes and produce new virions. The exact strategy adopted by each one of them is witnessed beautifully in the outstanding remodeling of the host cellular architecture during their life cycle.

While Single Particle reconstruction methods revealed the beauty of amazing symmetrical capsids in homogeneous samples, heterogeneous samples such as pleomorphic viruses, could only be studied by Electron Tomography (ET). The heterogeneous environment of the host and its remodeling takes place also in three dimensions. With the 3^rd spatial aspect lost in 2D projection images, ET will always remain the method of choice to study their life cycles (attachment, entry, replication, assembly and egress) in molecular detail.

Highlights

Archaeal viruses can surprise you! The lack of evolutionary relationship to other known viruses points to unique viral-host interaction sceneries. Sulfolobus islandicus filamentous virus (SIFV) is only one of them! In eukaryotes usually acquire envelopes inside the cell by budding through organelles. How is this taking place in Archaea that lack such organelles? SIFV was found to reach its full maturity (2 μm in length) and to be enveloped inside its host!

PNAS 2021 Vol. 118 No. 32 e2105540118

Newly synthesized Vaccinia membranes inside the eukaryotic host cell appear as short, curved units, named crescents. These develop into spheres where the viral DNA is packed. This step is critically depended on the viral scaffold protein D13. The proper assembly of the D13 scaffold layer around the convex side of the crescents and subsequently around the spheres is further fine tuned with the help of the Virus Membrane Associated Proteins (VMAPs). When the expression of the VMAP H7 is blocked, the D13 trimers instead of packing in the honeycomb lattice were found clustered together with short membranes of probable ER origin.

Anastasia was lucky enough to be one of Prof. N. J. Panopoulos’ PhD students at University of Crete, Heraklion (2003-2007). She fall in love with the bacterial type III secretion systems (T3SS), admiring the evolution of protein nanomachines as strong as the evolution of the structural biology field itself. Thanks to Prof. M.I. Kokkinidis she visited DESY numerous times to collect data both on Small Angle X-ray Scattering and protein crystallography beamlines. In 2009 Anastasia attended what she believes is the best course for large experimental systems ever: the HERCULES course in Grenoble, where she visited ESRF, ILL and Soleil for the first time. The same year she got an EMBO short term fellowship to visit the group of Dr. Andrea Dessen @IBS, Grenoble. Still committed to T3SS, she joined the lab of Prof. P. Sansonetti end of 2010 to use Electron Microscopy (EM) as the main research methodology. A quick and dirty postdoc at a different field (biologically and methodologically -wise) then followed. In 2016 she had the pleasure to return to the historical Electron Microscopy facility of I. Pasteur, Paris thanks to a LABEX grant and to Prof. J. Krijnse-Locker. She was inspired heavily by the academic software SerialEM and decided that the EM field deserves her full attention. In 2018 she was hired by Dr. Yaser Hashem @IECB Pessac, based on his ERC grant as an EM research engineer for cryoEM data collections @TALOS Arctica. She had the pleasure to be the first to also collect cryoET data @IECB. Although she loved to work in Hashem’s team, I. Pasteur finally offered her a permanent contract the same year. Anastasia is deeply thankful to all people she met during this journey.