Featured Research

from universities, journals, and other organizations

MicroRNAs Have Shaped The Evolution Of The Majority Of Mammalian Genes

Date:
November 29, 2005
Source:
Whitehead Institute for Biomedical Research
Summary:
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.

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.

Related Articles


"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."

###

This study was funded by the National Institutes of Health and the Howard Hughes Medical Institute.


Story Source:

The above story is based on materials provided by Whitehead Institute for Biomedical Research. Note: Materials may be edited for content and length.


Cite This Page:

Whitehead Institute for Biomedical Research. "MicroRNAs Have Shaped The Evolution Of The Majority Of Mammalian Genes." ScienceDaily. ScienceDaily, 29 November 2005. <www.sciencedaily.com/releases/2005/11/051129181931.htm>.
Whitehead Institute for Biomedical Research. (2005, November 29). MicroRNAs Have Shaped The Evolution Of The Majority Of Mammalian Genes. ScienceDaily. Retrieved December 18, 2014 from www.sciencedaily.com/releases/2005/11/051129181931.htm
Whitehead Institute for Biomedical Research. "MicroRNAs Have Shaped The Evolution Of The Majority Of Mammalian Genes." ScienceDaily. www.sciencedaily.com/releases/2005/11/051129181931.htm (accessed December 18, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Thursday, December 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

UN: Up to One Million Facing Hunger in Ebola-Hit Countries

UN: Up to One Million Facing Hunger in Ebola-Hit Countries

AFP (Dec. 17, 2014) Border closures, quarantines and crop losses in West African nations battling the Ebola virus could lead to as many as one million people going hungry, UN food agencies said on Wednesday. Duration: 00:52 Video provided by AFP
Powered by NewsLook.com
When You Lose Weight, This Is Where The Fat Goes

When You Lose Weight, This Is Where The Fat Goes

Newsy (Dec. 17, 2014) Can fat disappear into thin air? New research finds that during weight loss, over 80 percent of a person's fat molecules escape through the lungs. Video provided by Newsy
Powered by NewsLook.com
Why Your Boss Should Let You Sleep In

Why Your Boss Should Let You Sleep In

Newsy (Dec. 17, 2014) According to research out of the University of Pennsylvania, waking up for work is the biggest factor that causes Americans to lose sleep. Video provided by Newsy
Powered by NewsLook.com
Flu Outbreak Closing Schools in Ohio

Flu Outbreak Closing Schools in Ohio

AP (Dec. 17, 2014) A wave of flu illnesses has forced some Ohio schools to shut down over the past week. State officials confirmed one pediatric flu-related death, a 15-year-old girl in southern Ohio. (Dec. 17) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins