Scientists at Monash University's Biomedicine Discovery Institute (BDI) have identified a new mechanism used by Henipaviruses in infection, and potential new targets for antivirals to treat them. The researchers believe their findings may also apply to other dangerous viruses.
Henipaviruses are among the deadliest of viruses and have no effective treatments, according to the researchers. The viruses include Hendra, lethal to humans and horses, and the Nipah virus, a serious threat in East and Southeast Asia. They are on the World Health Organization Blueprint list of priority diseases needing urgent research and development action.
The BDI study (“Viral regulation of host cell biology by hijacking of the nucleolar DNA-damage response”) was published in Nature Communications.
“Recent studies indicate that nucleoli play critical roles in the DNA-damage response (DDR) via interaction of DDR machinery including NBS1 [nibrin] with nucleolar Treacle protein, a key mediator of ribosomal RNA (rRNA) transcription and processing. Here, using proteomics, confocal and single molecule super-resolution imaging, and infection under biosafety level-4 containment, we show that this nucleolar DDR pathway is targeted by infectious pathogens,” write the investigators.
“We find that the matrix proteins of Hendra virus and Nipah virus, highly pathogenic viruses of the Henipavirus genus in the order Mononegavirales, interact with Treacle and inhibit its function, thereby silencing rRNA biogenesis, consistent with mimicking NBS1–Treacle interaction during a DDR. Furthermore, inhibition of Treacle expression/function enhances henipavirus production. These data identify a mechanism for viral modulation of host cells by appropriating the nucleolar DDR and represent, to our knowledge, the first direct intranucleolar function for proteins of any mononegavirus.”
A collaboration of scientists, led by BDI's Gregory Moseley, Ph.D., head of the viral pathogenesis laboratory found that Henipaviruses hijack a mechanism used by cells to counter DNA damage and prevent harmful mutations, important in diseases such as cancer. Dr. Moseley said it was already known that the viruses send a particular protein into the nucleolus, but it wasn't known why it did this. He added that the team showed that this protein interacted with a cell protein (Treacle) that is an important part of the DNA-damage response machinery. This inhibited Treacle function, which appears to enhance henipavirus production.
"What the virus seems to be doing is imitating part of the DNA damage response," Dr. Moseley says. "It is using a mechanism your cells have to protect you against things like aging and mutations that lead to cancer. This appears to make the cell a better place for the virus to prosper.”
According to Dr. Moseley, it is possible that blocking the virus from doing this may lead to the development of new antiviral therapies. "We identified a new way that viruses change the cell, by using the very same machinery that the cell normally uses to protect itself from diseases like cancer," he explains.
The researchers are now trying to work out exactly how changing the DNA damage response through Treacle is useful to henipavirus and other dangerous viruses.