Featured Research

from universities, journals, and other organizations

The fight against genome parasites

Date:
June 4, 2013
Source:
Institute of Molecular Biotechnology
Summary:
In the gonads of animals, genome parasites such as transposons pose a serious threat to evolutionary fitness. With their ability to bounce around in the genome, they often cause dangerous mutations. To protect genomic integrity, animals evolved a sophisticated mechanism – the so called piRNA pathway – to silence the deleterious transposons. Not much is known about the molecular processes and the involved factors that constitute the piRNA pathway. Researchers have now identified about 50 genes, that play important roles in the piRNA pathway of the fruitfly Drosophila melanogaster.

Drosophila ovaries.
Credit: Image courtesy of Institute of Molecular Biotechnology

In the gonads of animals, genome parasites such as transposons pose a serious threat to evolutionary fitness. With their ability to bounce around in the genome, they often cause dangerous mutations. To protect genomic integrity, animals evolved a sophisticated mechanism -- the so called piRNA pathway -- to silence the deleterious transposons. Not much is known about the molecular processes and the involved factors that constitute the piRNA pathway. Researchers at the Institute of Molecular Biotechnology (IMBA) of the Austrian Academy of Sciences (ΦAW) in Vienna have now identified ~50 genes, that play important roles in the piRNA pathway of the fruitfly Drosophila melanogaster.

With roughly 50%, the human genome is densely populated with genome parasites, and so is the DNA of other animals, plants and fungi. Many of these selfish DNA elements are able to freely move around in the host's genetic material. They are referred to as transposons and their mobility causes DNA breaks and mutations that can lead to severe genome damage. Although they are harmful, most organisms do not specifically eliminate transposons from their DNA. Such a massive intervention might bear too much of a risk for germ cell genomes and hence a species reproductive fitness.

To deal with the potential dangers, plants and animals possess defense systems -- also seen as sort of a 'genome immune system'. In all cases, these are based on small RNA silencing mechanisms and hence date probably back to the early days of eukaryotic evolution. The ancient silencing systems are able to selectively interfere with transposon expression preventing them from causing damage.

In animals, the most prominent of these silencing pathways is the so-called piRNA pathway. At its core act so-called RNA induced silencing complexes (RISC) that are composed of PIWI proteins bound to 22-30nt long piRNAs. Via the small RNA, PIWI complexes recognize transposon RNAs and this induces degradation of the transposon RNA and feeds back negatively on the encoding locus on the host DNA to inhibit transposon transcription.

Fly library as goldmine of knowledge

For their screen, Brennecke and his group took advantage of the Vienna Drosophila RNAi Center (VDRC) library, a collection of ~30.000 fly stocks each allowing the silencing of a specific gene in a desired cell type. The VDRC library was established at the IMBA/IMP campus under leadership of Barry Dickson and Krystyna Keleman and is now run by the Campus Support Facility (CSF). From there, flies are sent out to institutes and research centers all over the globe. "The Vienna fly library is a worldwide unique resource that allows systematic studies of gene function in virtually every aspect of fruitfly biology," compliments Brennecke. In their two years of work, Brennecke and his group discovered around 50 genes that are important for a fully functional piRNA pathway. Dominik Handler, PhD student in Brennecke's lab and first author of the study, explains: "For many of the identified genes, orthologous genes can be identified in the human genome, too. Our results will therefore have a broad impact on the general understanding of this transposon silencing system." Some of the identified genes are required for the biogenesis of piRNAs, but others connect the defense system to basic processes such as mitochondria-metabolism, RNA transport, transcription or chromatin-biology.

Signalling-pathway with great potential

The obtained results set the stage for multiple lines of future investigations, underlines Brennecke. The identified factors will play key roles in understanding the mechanistic framework of the pathway, but they will also be unique entry points into understanding how this silencing system is embedded into the general process of oogenesis. Key question along those lines are how piRNAs are passed from generation to generation and what evolutionary benefit the host might have from transposons. Brennecke is fascinated by the close interplay between possible advantages and dangers that transposons and other repetitive sequences have for host genome regulation. He is confident: "Core concepts of the piRNA pathway are highly conserved amongst organisms. I have no doubt, that our results will have far reaching implications for the understanding of genome evolution and possibly even aspects of human medicine."


Story Source:

The above story is based on materials provided by Institute of Molecular Biotechnology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Dominik Handler, Katharina Meixner, Manfred Pizka, Kathrin Lauss, Christopher Schmied, Franz Sebastian Gruber, Julius Brennecke. The Genetic Makeup of the Drosophila piRNA Pathway. Molecular Cell, 2013; DOI: 10.1016/j.molcel.2013.04.031

Cite This Page:

Institute of Molecular Biotechnology. "The fight against genome parasites." ScienceDaily. ScienceDaily, 4 June 2013. <www.sciencedaily.com/releases/2013/06/130604094524.htm>.
Institute of Molecular Biotechnology. (2013, June 4). The fight against genome parasites. ScienceDaily. Retrieved July 29, 2014 from www.sciencedaily.com/releases/2013/06/130604094524.htm
Institute of Molecular Biotechnology. "The fight against genome parasites." ScienceDaily. www.sciencedaily.com/releases/2013/06/130604094524.htm (accessed July 29, 2014).

Share This




More Plants & Animals News

Tuesday, July 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Ebola Virus Threatens West Africa

Deadly Ebola Virus Threatens West Africa

AP (July 28, 2014) — West African nations and international health organizations are working to contain the largest Ebola outbreak in history. It's one of the deadliest diseases known to man, but the CDC says it's unlikely to spread in the U.S. (July 28) Video provided by AP
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) — Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) — The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) — A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) 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:
from the past week

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