Researchers describing a key protein for Epstein Barr virus infection; the study 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 causing 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.
But this protein is find only in herpesviruses, these inhibitors would be virus-specific and may be less toxic for humans. All herpesviruses have a similar infection mechanism. Having entering the cell and reached the nucleus, the viruses release their DNA, which can remain latent for years until certain conditions trigger its replication.
Epstein Barr virus infection
Herpesviridae is a vast family of enveloping DNA viruses; that including eight distinct human pathogens, responsible for diseases that range from almost asymptomatic to severe and life-threatening. Epstein-Barr virus infects B-cells and epithelial cells, causing infectious mononucleosis, as well as a number of cancers. Epstein-Barr infection cannot be curing since neither vaccine nor antiviral drug treatments are available.
After this process, DNA is then introducing 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. The researchers have also characterised the structure of the portal protein in bacteriophage T7.
DNA packaging system
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. 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. To study the structure of this protein, the researchers used both synchrotron X-ray diffraction and high-resolution electron cryomicroscopy. Both studies were performing in collaboration; with the CNB-CSIC and the University of Oxford (UK).