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 Transport of molecular motors into cilia
28.03.2017 | Aarhus University

nachricht Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers shoot for success with simulations of laser pulse-material interactions

29.03.2017 | Materials Sciences

Igniting a solar flare in the corona with lower-atmosphere kindling

29.03.2017 | Physics and Astronomy

As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation

29.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>