Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists track ’stealth’ DNA elements in primate evolution

02.05.2005


New theory contends that long-lived, quiescent retroelements are a major driving force in human genome evolution



Louisiana State University scientists in the Department of Biological Sciences have unraveled the details of a 25-million-year-old evolutionary process in the human genome. Specific DNA sequences that appear to have persisted in a latent state for long periods of time may not be simply lying dormant. Instead, the researchers say that these elements have played a crucial role in human evolution by surreptitiously spawning hyperactive progeny copies, giving rise to the most abundant family of DNA elements in the human genome: Alu elements. The study, which was led by LSU scientist Dr. Mark A. Batzer, provides the first strong mechanistic evidence for the evolution of Alu elements to date. It appears in the May issue of the journal Genome Research.

Alu elements are short, 300-nucleotide-long DNA sequences capable of copying themselves, mobilizing through an RNA intermediate, and inserting into another location in the genome. Over evolutionary time, this retrotransposition activity has led to the generation of over one million copies of Alu elements in the human genome, making them the most abundant type of sequence present. Because Alu elements are so abundant, comprising approximately 10% of the total human genome, they have been thoroughly characterized in terms of their origin and sequence composition. What has remained elusive to scientists, however, are the actual mechanisms by which these elements persist and propagate over time to influence human evolution.


In an attempt to understand these mechanisms, Dr. Batzer and his colleagues examined a subfamily of Alu elements in the human genome known as the AluYb lineage, and compared these elements to those in the genomes of other primate species, including chimpanzees, bonobos, gorillas, orangutans, gibbons and siamangs. The AluYb subfamily accounts for approximately 40% of all human-specific Alu elements and is currently one of the most active Alu lineages in the human genome. Some AluYb elements are still actively mobilizing in the human genome, causing insertion mutations that have led to the development of a number of heritable diseases.

Dr. Batzer’s team demonstrated that some AluYb subfamily members have orthologs in all primate genomes tested, which dates the AluYb linage to an origin approximately 18-25 million years ago. Their results also indicated that the AluYb subfamily underwent a major species-specific expansion in the human genome during the past 3-4 million years. This apparent 20-million-year stretch of retrotranspositional quiescence, followed by a sudden outburst of human-specific retrotransposition activity in the past few million years, led Dr. Batzer and colleagues to formulate a new theory for the evolution of Alu elements, termed the "stealth driver" model. In the "stealth driver" model, low-activity Alu elements are maintained in low-copy number for long periods of time and occasionally produce short-lived hyperactive progeny that contribute to the formation and expansion of Alu elements in the human genome.

To date, the most widely accepted theory of Alu retrotransposition is called the "master gene" theory, which asserts that the majority of Alu retrotransposition activity is driven by a small number of hyperactive "master" sequences. In this model, mutations occurring in the "master" copies have rendered themselves capable of substantial propagation and persistence over time. However, prior evidence from the Ya5 subfamily indicated that at least some "master" Alu elements may persist in low-copy numbers for long periods of evolutionary time without retrotranspositional activity, suggesting that the mechanisms of Alu expansion may be much more complex. These observations led Dr. Batzer and his co-workers to examine the Yb subfamily of Alu elements, to demonstrate that the Yb subfamily has a similar evolutionary pattern to that of AluYa5, and to formulate the "stealth driver" hypothesis for the evolution of these Alu elements.

"In contrast to ’master’ genes, ’stealth drivers’ are not responsible for generating the majority of new Alu copies, but rather for maintaining genomic retrotransposition capacity over extended periods of time," Batzer explains. "By generating new Alu copies at a slow rate, a ’stealth driver’ may occasionally spawn progeny elements that are capable of much higher retrotransposition rates. These hyperactive progeny elements may act as ’master’ genes for the amplification of Alu subfamilies and are responsible for producing the majority of the subfamily members. Due to their high retrotransposition levels, however, they are likely to be rapidly purged from human populations through natural selection."

Dr. Batzer, principal investigator on the study, is the George C. Kent Professor of Life Sciences in the Department of Biological Sciences at LSU. Co-first authors on the manuscript, Kyudong Han and Jinchuan Xing, are graduate students in the Department of Biological Sciences at LSU. LSU graduate students Hui Wang and Dale Hedges, along with postdoctoral fellows Drs. Randall Garber and Richard Cordaux, also share authorship on the paper.

Maria A. Smit | EurekAlert!
Further information:
http://www.cshl.edu

More articles from Life Sciences:

nachricht Antimicrobial substances identified in Komodo dragon blood
23.02.2017 | American Chemical Society

nachricht New Mechanisms of Gene Inactivation may prevent Aging and Cancer
23.02.2017 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>