Scientists at the Institute for Research in Biomedicine (IRB Barcelona) and the Molecular Biology Institute of Barcelona (IBMB-CSIC) have published a study in the journal Nature Communications revealing the structure of a key protein, known as a portal, in Epstein-Barr virus infection.

The Epstein-Barr virus, which belongs to the herpesvirus family, is one of the most widespread human viruses and the main cause of infectious mononucleosis (also known as glandular fever). In addition, it causes several kinds of cancer, including Burkitt and Hodgkins lymphoma, stomach cancer and nasopharyngeal cancer, as well as several autoimmune diseases. There is currently no treatment for infections caused by this virus.

“Understanding the structure of the portal protein could prove useful for the design of inhibitors for the treatment of herpesvirus infections such as Epstein-Barr. Also, given that this protein is found only in herpesviruses, these inhibitors would be virus-specific and may be less toxic for humans,” says Miquel Coll, head of the Structural Biology of Protein & Nucleic Acid Complexes and Molecular Machines Lab at IRB Barcelona and professor at CSIC.

All herpesviruses have a similar infection mechanism. Having entered the cell and reached the nucleus, the viruses release their DNA, which can remain latent for years until certain conditions trigger its replication. After this process, DNA is then introduced into new viral capsids, thereby forming new viruses that can attack other cells. The portal protein is the route through which DNA enters the viral capsid and through which it leaves to infect cells.

In a second study recently published in the same journal, the researchers have alsocharacterised the structure of the portal protein in bacteriophage T7. This phage is a virus that infects only bacteria and, interestingly, its DNA packaging system resembles that used by herpesviruses.

“By solving the structure of the portal protein of bacteriophage T7, we have been able to infer how the portal from Epstein-Barr virus works,” explain Cristina Machón and Montserrat Fàbrega, postdoctoral fellows at IRB Barcelona and IBMB-CSIC, and first authors —together with Ana Cuervo, from the National Centre for Biotechnology (CNB-CSIC)—of the studies published.

“In both viruses, the portal protein comprises 12 subunits, forming a large mushroom-shaped structure, with a central channel through which DNA passes. This channel has a valve that regulates the entry and exit of the virus’ genetic material,” explains Coll.

To study the structure of this protein, the researchers used both synchrotron X-ray diffraction and high-resolution electron cryomicroscopy. Both studies were performed in collaboration with the CNB-CSIC and the University of Oxford (UK).

The studies were supported by the “Severo Ochoa” and “María de Maeztu” programmes of excellence, the “Ramón y Cajal” Programme of the Ministry of Science, Innovation and Universities, and the European projects iNEXT and Instruct-ERIC.

Reference articles:

Cristina Machón, Montserrat Fàbrega-Ferrer, Daming Zhou, Ana Cuervo, José L. Carrascosa, David I. Stuart and Miquel Coll

Atomic structure of the Epstein-Barr virus portal

Nature Communications (2019) DOI: 10.1038/s41467-019-11706-8

Ana Cuervo, Montserrat Fàbrega-Ferrer, Cristina Machón, José Javier Conesa, Francisco José Javier Fernández, Rosa Pérez-Luque, Mar Pérez-Ruiz, Joan Pous, María Cristina Vega, José L. Carrascosa and Miquel Coll

Structures of T7 bacteriophage portal and tail suggest a viral DNA retention and ejection mechanism

Nature Communications (2019) DOI: 10.1038/s41467-019-11705-9

About IRB Barcelona

Created in 2005 by the Generalitat de Catalunya (Government of Catalonia) and University of Barcelona, IRB Barcelona is a Severo Ochoa Centre of Excellence, a seal that was awarded in 2011. The institute is devoted to conducting research of excellence in biomedicine and to transferring results to clinical practice, thus improving people’s quality of life, while simultaneously promoting the training of outstanding researchers, technology transfer, and public communication of science. Its 25 laboratories and seven core facilities address basic questions in biology and are orientated to diseases such as cancer, metastasis, Alzheimer’s, diabetes, and rare conditions. IRB Barcelona is an international centre that hosts 400 employees and 32 nationalities. It is located in the Barcelona Science Park. IRB Barcelona forms part of the Barcelona Institute of Science and Technology (BIST) and the “Xarxa de Centres de Recerca de Catalunya” (CERCA).

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