Navigation Links
Virus uses tiny RNA to evade the immune system

In the latest version of the hide-and-seek game between pathogens and the hosts they infect, researchers have found that a virus appears to cloak itself with a recently discovered gene silencing device to evade detection and destruction by immune cells.

The report by Howard Hughes Medical Institute (HHMI) researchers in an article published in the June 2, 2005, issue of Nature may be the first to show how a virus uses the gene silencing machinery for its own infectious purposes.

In people, plants, and worms, hundreds of tiny RNA molecules can silence specific genes by interfering with larger messenger RNAs (mRNAs). That interference prevents mRNAs from making proteins. Scientists do not know which genes are hushed by the microRNAs in people, but the new study bolsters growing evidence that the little molecules can play important roles not only in normal human cells but in infected cells as well.

"A popular notion is that the whole system of generating small RNAs was designed to be a defense by cells against viruses. Our study shows that a virus can also adapt it to evade the immune response," said HHMI investigator Don Ganem, who is at University of California, San Francisco.

Ganem studies how viruses infect people and cause disease. When scientists found that RNA interference appeared to be a basic and widespread gene regulatory mechanism, "it became clear that such a fundamental pathway could of course be pirated by a virus," said postdoctoral fellow Adam Grundhoff, co-first author of the paper.

Thomas Tuschl, a newly selected HHMI investigator at The Rockefeller University, had already reported the existence of several microRNAs encoded by Epstein-Barr virus, although their functions were unknown. Grundhoff and co-first author Christopher Sullivan, a postdoctoral fellow in Ganem's lab, started their search for viral microRNAs with a small virus, known as SV40, in the belief that its diminutive size would make it easier to un derstand the functions of any microRNAs they found.

SV40 is a relatively harmless monkey virus that can cause kidney infections in its natural simian host. In rodents, however, it can cause cancer. Although the SV40 genome has been found in some human tumors, its role in human cancer has been debated. The virus is better known as a model system that has greatly contributed to major scientific advances about how genes work.

To launch their study, Grundhoff wrote a computer program to screen the SV40 genome for possible microRNA precursors. MicroRNAs are made from messenger RNA molecules with distinctive hairpin folds. The hairpin structure is diced into a microRNA segment that works with another complex to disable other messenger RNAs with complementary sequences.

Among several dozen predicted microRNAs, the top candidate turned out to be abundantly expressed in human cells infected with SV40.

Sullivan soon found the target of the plentiful SV40 microRNA. It effectively targeted the messenger RNA for a protein known as T antigen, leading to its cleavage. "SV40 may be the world's most studied virus," Sullivan said, "and T antigen is its most studied part."

When SV40 enters a cell, it produces T antigen, which functions to trigger viral DNA replication. Unfortunately for the virus, T antigen also serves as a target for immune (T) cells, which can destroy infected cells and prevent the virus from spreading.

Conveniently, the microRNA that targets T antigen is made late in the infectious cycle, just when T antigen is no longer essential for virus replication. Further experiments showed that cytotoxic immune cells were more likely to kill cells infected with a mutant virus that cannot make the microRNA than the normal virus. Thus, microRNA-induced reductions in T antigen expression promote escape from antiviral T cells without affecting virus growth.

"Viruses can use the host RNA inference machinery, which is often s peculated to have evolved as an antiviral mechanism, to generate small RNAs that serve their own purposes -- the latest chapter in the long cat-and-mouse game known to virologists as host-virus coevolution," the researchers conclude in their Nature article.


'"/>

Source:Howard Hughes Medical Institute


Related biology news :

1. Scientists Replicate Hepatitis C Virus in Laboratory
2. Study: Soap And Water Work Best In Ridding Hands Of Disease Viruses
3. Mayo Clinic Researchers Create Obedient Virus; First Step To Use Measles Virus Against Cancer
4. Norovirus, AIDS vaccine and Hepatitis Virus
5. Virus-host interactions at sea effect global photosynthesis
6. How A Latent Virus Eludes Immune Defenses
7. Secrets to antibodys success against West Nile Virus surprise scientists
8. “Hitchhiking?Viruses as Cancer Drug Delivery System
9. Virus chip detects new virus in prostate tumors
10. Virus has catastrophic affect on red squirrels, research shows
11. New strategy developed to combat West Nile Virus
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:3/29/2017)...  higi, the health IT company that operates the ... , today announced a Series B investment from ... The new investment and acquisition accelerates higi,s strategy to ... population health activities through the collection and workflow integration ... collects and secures data today on behalf of over ...
(Date:3/27/2017)... , March 27, 2017  Catholic Health ... and Management Systems Society (HIMSS) Analytics for achieving ... Adoption Model sm . In addition, CHS previously ... U.S. hospitals using an electronic medical record (EMR). ... its high level of EMR usage in an ...
(Date:3/24/2017)... , Mar 24, 2017 Research and ... Access System Market Analysis & Trends - Industry Forecast to 2025" ... ... to grow at a CAGR of around 15.1% over the next ... This industry report analyzes the market estimates and forecasts for all ...
Breaking Biology News(10 mins):
(Date:10/10/2017)... ... October 10, 2017 , ... For the ... won a US2020 STEM Mentoring Award. Representatives of the FirstHand program travelled to ... Experience from US2020. , US2020’s mission is to change the trajectory of STEM ...
(Date:10/10/2017)... ... October 10, 2017 , ... USDM ... firm for the life sciences and healthcare industries, announces a presentation by Subbu ... , The presentation, “Automating GxP Validation for Agile Cloud Platforms,” will present a ...
(Date:10/9/2017)... ... October 09, 2017 , ... At its national board meeting in North ... in Harvard University’s Departments of Physics and Astronomy, has been selected for membership in ... winning team for the 2015 Breakthrough Prize in Fundamental physics for the discovery of ...
(Date:10/7/2017)... ... October 06, 2017 , ... ... its ProxiMeta™ Hi-C metagenome deconvolution product, featuring the first commercially available Hi-C ... software to perform Hi-C metagenome deconvolution using their own facilities, supplementing the ...
Breaking Biology Technology: