Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Where ’jumping genes’ fear to tread

06.01.2006


Researchers identify large tracks of DNA refractory to mobile element insertion



Scientists from the University of Queensland report in the journal Genome Research that large segments of the human genome are conspicuously devoid of ubiquitous mobile DNA elements called transposons. The locations of these regions are highly conserved among mammalian species and are enriched in genes crucial for the regulation of developmental processes.

Transposons, often called "jumping genes," are DNA sequences that have the capacity to move from one chromosomal site to another. More than three million copies of transposons have accumulated in humans throughout the course of evolution and now comprise an estimated 45% of the total DNA content in the human genome.


These mobile genetic elements are scattered throughout the human genome – separated, on average, by only 500 base pairs. But Dr. John Mattick’s laboratory at the University of Queensland, Australia, identified long tracks of genomic segments (greater than 10 kilobases in length) that lack transposable elements. His team identified 860 such sequences in humans, 993 in mice, and 559 in opossums. They named these segments TFRs, or transposon-free regions.

"Strikingly," says Mattick, "many TFRs in the human genome occur in the same position in the mouse and opossum genomes, despite the fact that transposons entered each lineage independently, after each species diverged from a common ancestor. It appears that many TFRs are evolutionarily conserved features that existed prior to – and have been largely maintained since – the divergence of eutherian mammals and marsupials approximately 170 million years ago."

The opossum was chosen for inclusion in the analysis because it is a marsupial that has a similar load of transposable elements compared to mice and humans but is evolutionarily distant from the two species. In contrast, the genomes of chicken and fish, which diverged from humans more than 300 million years ago, do not have a significant density of transposons.

Given the strong evolutionary conservation of the TFRs, Mattick’s group hypothesized that they are regions of significant biological importance. Upon further characterizing the TFRs, they discovered that many (85%) overlapped at least one annotated gene and that almost all (94%) overlapped at least one known RNA transcript. In addition, the TFRs were enriched in microRNAs, in genes that encode proteins with putative DNA-binding activity, and in genes that are involved in developmental processes. Another striking feature of TFRs was that they are associated with ultra-conserved regions, or genomic segments longer than 200 base pairs with 100% identity between human, mouse, and rat. All of these observations strongly support an important role for TFRs in critical biological processes.

"The majority of the TFRs lie outside of protein-coding sequences, so they presumably represent regions of regulatory information or RNA transcripts that cannot be disrupted. However, it’s difficult to explain mechanistically the requirement of 10 or more kilobases of uninterrupted sequence in terms of the current paradigms of transcriptional regulation," explains Mattick. "It appears that TFRs might be the passive signatures of one or more poorly understood mechanisms of gene regulation that operate in higher organisms, suggesting a wider role for noncoding sequences than has hitherto been appreciated."

The work was conducted under Mattick’s guidance by graduate students Cas Simons and Michael Pheasant, as well as by Dr. Igor Makunin, a postdoctoral researcher.

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

More articles from Life Sciences:

nachricht Toward a 'smart' patch that automatically delivers insulin when needed
18.01.2017 | American Chemical Society

nachricht 127 at one blow...
18.01.2017 | Stiftung Zoologisches Forschungsmuseum Alexander Koenig, Leibniz-Institut für Biodiversität der Tiere

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>