Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


MicroRNAs have shaped the evolution of the majority of mammalian genes


RNA continues to shed its reputation as DNA’s faithful sidekick. Now, researchers in the lab of Whitehead Institute Member David Bartel have found that a class of small RNAs called microRNAs influence the evolution of genes far more widely than previous research had indicated.

"MicroRNAs are affecting the majority of protein-coding genes, either at a functional level or an evolutionary level," says Andrew Grimson, a post-doctoral fellow in Bartel’s lab.

In order to make a protein, a gene codes for a specific molecule called messenger RNA, or mRNA. Each mRNA molecule contains a blueprint for making a protein. A microRNA can bind to a short sequence on a targeted mRNA and suppress protein production.

In a paper published last January in the journal Cell, Bartel’s lab, in collaboration with Chris Burge’s lab at MIT, presented evidence that one third of human genes are regulated by microRNAs. In this new study, published online Nov. 24 in Science, the researchers demonstrate that microRNAs affect the expression or evolution of the majority of human genes.

Nearly all genes, the authors explain, contain short sequences that match portions of microRNAs. Some of these potential microRNA target sites are evolutionarily "conserved," meaning that they show up in the same spot on the same gene across species as disparate as the mouse and the chicken. The authors of last January’s Cell paper showed that thousands of human genes contain microRNA sites that are conserved in this way. To the extent that evolution has preserved these sites more than would be expected by chance, scientists have regarded them as sites that microRNAs target.

But is a matching sequence all that’s required for microRNA targeting and gene regulation, and do nonconserved sites also have the potential to disrupt protein production?

In the new study, scientists in the Bartel lab designed an experiment that zeroed in on these nonconserved targets. Grimson took mRNAs whose target sequences were not conserved and exposed them to microRNAs, which latched on without a problem. The experiment proved that a matching sequence is generally sufficient to disrupt mRNA’s ability to make protein.

But while Grimson showed that, at least in the lab, microRNAs could regulate mRNAs with nonconserved sites, the researchers still didn’t know the extent to which nonconserved mRNAs coexisted with their matching microRNAs in the natural cell environment. To answer this question, the researchers turned to gene expression patterns of different types of mouse cells.

Kyle Kai-How Farh, a graduate student in Bartel’s lab, found that mRNAs with nonconserved sites were generally absent in cells with corresponding microRNAs--more absent than statistical models suggested. The researchers concluded that over the course of evolution many mRNAs, in order to maintain their functions and ensure fitness of the organism, have quickly lost sites that pair up with microRNAs.

In addition to the thousands of cases where genes have avoided microRNA targeting, Farh also investigated the opposite extreme, cases where genes have maintained microRNA target sites over the course of evolution. He found that as immature muscle cells stop dividing and become mature muscle cells, microRNAs are activated and suppress genes that are no longer needed at such high levels in the mature muscle. "Many of these evolutionarily conserved microRNA targets are known to be active in the processes of cell proliferation, development, and cancer," says Farh. "Our genomes have good reason to maintain the microRNA targeting sites necessary for turning down these genes at the appropriate place and time."

An emerging idea is that microRNAs often act to reduce the quantity of protein a gene produces without shutting it off all together. "We think the microRNAs are sometimes having what you can call a dampening effect," says Bartel, who is also a Howard Hughes Medical Institute investigator and MIT professor of biology. "They appear to be helping cells achieve optimal levels of proteins."

"MicroRNAs are leaving an evolutionary footprint on the majority of the mammalian genome," says Grimson. "Some genes are trying to preserve beneficial microRNA sites and others are evolving in order to avoid developing harmful ones."

David Cameron | EurekAlert!
Further information:

More articles from Studies and Analyses:

nachricht Diagnoses: When Are Several Opinions Better Than One?
19.07.2016 | Max-Planck-Institut für Bildungsforschung

nachricht High in calories and low in nutrients when adolescents share pictures of food online
07.04.2016 | University of Gothenburg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

First results of NSTX-U research operations

26.10.2016 | Physics and Astronomy

UCI and NASA document accelerated glacier melting in West Antarctica

26.10.2016 | Earth Sciences

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

More VideoLinks >>>