[Press release] Jumping genes have essential biological functions

From the 19 February 2015 EurekAlert!

“Alu” sequences are small repetitive elements representing about 10% of our genome. Because of their ability to move around the genome, these “jumping genes” are considered as real motors of evolution. However, they were considered for a long time as “junk” DNA, because, although they are transcribed into RNA, they encode no proteins and do not seem to participate actively in the cell’s functions. Now, the group of Katharina Strub, professor at the Faculty of Science of the University of Geneva (UNIGE), Switzerland, has uncovered two key functions of Alu RNAs in human cells, which are the subject of two different articles published in Nucleic Acids Research. Alu RNA can bind to specific proteins forming a complex called Alu RNP. On the one hand, this complex allows the cells to adapt to stress caused for example by chemical poisoning or viral infection. On the other hand, the same complex plays a role in protein synthesis by regulating the number of active ribosomes, suggesting that it could be part of the innate system of cellular defense against certain viruses.

 

‘Junk DNA’ can sense viral infection

This image shows a consensus secondary structure for a ncRNA family called mascRNA-menRNA. The colouring gives an indication of the sequence conservation. (Photo credit: Wikipedia)

[Well, another thing to unlearn from biology classes in the late 70’s…. the DNA that doesn’t seem to be doing anything isn’t junk after all!]

From the 25 April 2012 article at EurekaAlert

Promising tool in the battle between pathogen and host, Tel Aviv University research confirms

Once considered unimportant “junk DNA,” scientists have learned that non-coding RNA (ncRNA) — RNA molecules that do not translate into proteins — play a crucial role in cellular function. Mutations in ncRNA are associated with a number of conditions, such as cancer, autism, and Alzheimer’s disease.

Now, through the use of “deep sequencing,” a technology used to sequence the genetic materials of the human genome, Dr. Noam Shomron of Tel Aviv University’s Sackler Faculty of Medicine has discovered that when infected with a virus, ncRNA gives off biological signals that indicate the presence of an infectious agent, known as a pathogen. Not only does this finding give researchers a more complete picture of the interactions between pathogens and the body, but it provides scientists with a new avenue for fighting off infections.

His findings have been published in the journal Nucleic Acid Research.

Another battleground between pathogen and host

“If we see that the number of particular RNA molecules increases during a specific viral infection, we can develop treatments to stop or slow their proliferation,” explains Dr. Shomron.

In the lab, the researchers conducted a blind study in which some cells were infected with the HIV virus and others were left uninfected. Using the deep sequencer, which can read tens of millions of sequences per experiment, they analyzed the ncRNA to discover if the infection could be detected in non-coding DNA materials. The researchers were able to identify with 100% accuracy both infected and non-infected cells — all because the ncRNA was giving off significant signals, explains Dr. Shomron.

These signals, which can include either the increase or decrease of specific ncRNA molecules within a cell, most likely have biological significance, he says. “With the introduction of a pathogen, there is a reaction in both the coding and non-coding genes. By adding a new layer of information about pathogen and host interactions, we better understand the entire picture. And understanding the reactions of the ncRNA following infection by different viruses can open up the battle against all pathogens.”

Finding an “Achilles heel” of infections

The researchers believe that if an ncRNA molecule significantly manifests itself during infection by a particular pathogen, the pathogen has co-opted this ncRNA to help the pathogen devastate the host — such as the human body. To help the body fight off the infection, drugs that stop or slow the molecules’ proliferation could be a novel and effective strategy.

This new finding allows researchers to develop treatments that attack a virus from two different directions at once, targeting both the coding and non-coding genetic materials, says Dr. Shomron. He suggests that ncRNA could prove to be the “Achilles heel” of pathogens.

Dr. Shomron and his team of researchers developed new software, called RandA, which stands for “ncRNA Read-and-Analyze,” that performs ncRNA profiling and analysis on data generated through deep sequencing technology. It’s this software that has helped them to uncover the features that characterize virus-infected cells.