Navigation Links
MicroRNA helps prevent tumors

A microRNA directly regulates a gene implicated in human cancers, researchers from Whitehead Institute and Massachusetts Institute of Technology report in the February 22nd online issue of Science.

MicroRNAs are tiny snippets of RNA that can repress activity of a gene by targeting the gene's messenger RNA (which copies DNA information and starts the process of protein production).

The first microRNA was discovered in 1993, in worms. It took seven years for the second one to be found, also in worms, but then the floodgates burst. Many microRNAs now have been found in diverse plants and animals, including hundreds in humans. Moreover, microRNAs found in mammals regulate over a third of the human genome, as shown in a 2005 study by the lab of Whitehead Member and Howard Hughes Medical Institute Investigator David Bartel and colleagues.

But given the wealth of microRNAs, and the ability of individual microRNAs to target hundreds of genes, researchers have struggled to show the biological impact of a particular microRNA on a particular target in mammals (although such connections have been shown in plants, worms and flies). Several groups have demonstrated that over-expression or under-expression of a microRNA can play a role in certain cancers, but have not clarified the genes responsible.

Looking to find a promising target for an individual microRNA, Christine Mayr, a postdoctoral researcher in the Bartel lab, picked Hmga2, a gene that is defective in a wide range of tumors.

In these tumors, the protein-producing part of the Hmga2 gene is cut short and replaced with DNA from another chromosome. Biologists have mostly focused on the shortened protein as the possible reason that the cells with this DNA swap became tumors. But this DNA swap removes not only the gene's protein-producing regions but also those areas that don't code for protein. And these non-protein-producing regions contain the elements that microRNAs rec ognize.

It turns out that in the non-protein-producing region, Hmga2 has seven sites that are complementary to the let-7 microRNA, a microRNA expressed in the later stages of animal development. Mayr wondered whether loss of these let-7 binding sites, and therefore loss of regulation by let-7 of Hmga2, might cause over-expression of Hmga2 that in turn would result in tumor formation.

To find out, Mayr created a series of Hmga2 in which various numbers of let-7 sites were destroyed. She found clear evidence that when exposed to let-7, the fewer sites that were intact, the more protein was produced.

Next, she tested whether disrupting let-7's ability to repress Hmga2 would lead toward tumor creation. In a standard in vitro test of cancer-causing genes, colonies of mouse cells that expressed normal or shortened Hmga2 did not grow significantly, while cells in which Hmga2 contained disrupted let-7 sites did. In fact, the more that let-7 sites were damaged, the greater the number of colonies.

Mayr also worked with MIT assistant professor Michael Hemann to inject these cells in mice with a compromised immune system. The scientists found that the mice with cells that expressed the version of Hmga2 with the disrupted let-7 sites developed tumors.

Overall, the results highlight a new mechanism for cancer formation. Hmga2, and perhaps certain other genes that are normally regulated by microRNAs, can help give rise to tumors if a mutation in the gene disrupts the microRNA's ability to regulate it. In addition, the results show that the interaction of one microRNA with one of its target genes can produce a certain trait in mammals. This is important because scientists are only beginning to learn the functions of microRNAs in animals.

"Because hundreds of human genes appear to be regulated by the let-7 microRNA, we were afraid we wouldn't see any difference when we changed only one of these target genes," says Dav id Bartel, who is also an MIT biology professor. "Seeing the difference encourages us to explore the biological importance of other examples of microRNA regulation."
'"/>

Source:Whitehead Institute for Biomedical Research


Related biology news :

1. Yale Scientists Find MicroRNA Regulates Ras Cancer Gene
2. Cooperation is key—a new way of looking at MicroRNA and how it controls gene expression
3. MicroRNAs play a big part in gene regulation - and evolution
4. MicroRNA tweaks protein that controls early heart development
5. MicroRNAs have shaped the evolution of the majority of mammalian genes
6. MicroRNA gene that regulates lifespan found by Yale scientists
7. MicroRNA may have fail-safe role in limb development
8. MicroRNAs can be tumor suppressors
9. MicroRNAs as tumor suppressors
10. Jumping gene helps explain immune systems abilities
11. Protein helps regulate the genes of embryonic stem cells

Post Your Comments:
*Name:
*Comment:
*Email:


(Date:2/8/2017)...  Aware, Inc. (NASDAQ: AWRE ), a leading ... for its quarter and year ended December 31, 2016. ... $3.9 million compared to $6.9 million in the same quarter ... was $0.6 million compared to $2.6 million in the fourth ... 2016 was $0.5 million, or $0.02 per diluted share, which ...
(Date:2/8/2017)... Report Highlights The global biosurgery ... billion in 2016 at a compound annual growth rate ... Includes - An overview of the global market for ... from 2015 and 2016, and projections of compound annual ... market on the basis of product type, source, application, ...
(Date:2/7/2017)... LONG BEACH, New York , February 7, 2017 ... formerly known as ID Global Solutions Corporation [OTC: IDGS], ... identification, identity management and electronic transaction processing services, is ... a reorganization of the Company. Effective January ... Chairman of the Board of Directors, CEO and President. ...
Breaking Biology News(10 mins):
(Date:2/24/2017)... ... 24, 2017 , ... Chef Jodi Abel has returned from her three-week ... cities, she gained a number of delicious recipes and new techniques to share with ... Africa’s Western Cape province. It is internationally renowned for its incredible wine farms, ...
(Date:2/24/2017)... DIEGO , Feb. 24, 2017  Aethlon Medical, ... following note authored by its Chairman and CEO, ... at the Munich Security Conference last Saturday, Bill ... virus could kill more people than nuclear weapons. Mr. ... U.S. and U.K. intelligence agencies, that scientific terrorists have ...
(Date:2/24/2017)... , Feb. 24, 2017  Driven by ... biotechnology are now the fastest growing categories, finds ... Specialty Actives in Personal Care: Multi-regional Market Analysis ... and management consulting firm Kline. "Biotechnology ... that make them more effective for skin and ...
(Date:2/24/2017)... ... ... FireflySci, Inc is an explosive small business that continues to grow at ... their powerful cuvette and spectrophotometer calibration to the spectroscopy world. Now ... as they add yet another mark on the global map. , With distributors in ...
Breaking Biology Technology: