RZPD develops highly efficient products for genome research: siRNA resources for gene silencing

Berlin (January 14, 2004) - Scientists at the RZPD - Resource Center for Genome Research - recently developed an efficient method for the specific inhibition of gene functions by means of ribonucleic acids (RNAs). Such inhibitions are important for the identification of new target molecules for innovative medicaments. Currently, so-called small interfering RNAs (siRNAs) are the method of choice to "knock-down" the function of particular genes (gene silencing) thereby offering clues about which genes are responsible for the expression of a particular bodily function. In part the application of these molecules was proven to be inefficient. Furthermore, their chemical synthesis is very expensive and their use in high-throughput experiments is uneconomical. The RZPD has now presented a method by which efficient siRNAs can be synthesized economically. Starting point are more than 2,300 different and highly specific long double stranded DNA molecules (dsDNAs). These are degraded in a two-step enzymatic reaction into the desired siRNA molecules. At present these molecules are tested in model experiments in co-operation with the Max-Planck-Institute for Molecular Cell Biology and Genetics, Dresden.

The RZPD is continuously expanding existing siRNA resources. It is estimated that by the end of 2004 some 36,000 gene-specific products for human applications will be available. In addition to this the RZPD is developing respective material for mouse and rat, which will be available this spring.

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Background
Throughout the scientific community so-called "RNA interference" or RNAi is a renowned method for the validation, respectively identification, of novel target molecules for medically active compounds. In 2003 the journal Science even named the discovery of siRNAs and the related phenomenon of RNA interference the scientific breakthrough of the year. These molecules are exceptionally suited as means for the inhibition of specific gene products in functional genetics (Gene Silencing Tool), as well as promising novel therapeutics.

An important characteristic of the mechanism is the processing of long dsRNAs into short fragments of 21-23 nucleotides, the so-called small interfering RNAs (siRNAs) by the Dicer enzyme. Together with a protein complex the siRNA forms the RNA induced Silencing Complex (RISC), which binds the mRNA and cuts it in the centre of the siRNA. The mRNA degradation leads to post-transcriptional "gene silencing".

Originally "knock-down" in human, murine and rat cells was described for 21bp-dsRNAs. However, the use of which has three substantial disadvantages: I) an uncertain success rate (in general 2-3 different siRNA oligos are required to achieve the "knock-down" of one gene), II) quite often the efficiency is very low, and III) the costs for siRNA oligos quickly soar to several hundred euros per gene, thereby ruling out genome-wide screening in high-throughput experiments.

Therefore the RZPD has worked for some time on an alternative way of accomplishing "gene silencing", i.e. the use of in vitro transcription and recombinant RNA-digesting enzymes for the production of functional siRNAs. To achieve this, gene-specific products for some 36,000 Unigene Clusters were manufactured and verified. They were represented by PCR products, which were amplified using two gene-specific primers per gene, avoiding repetitive or conserved sequences. T7 promoters were added to convert these dsDNAs into dsRNAs by in vitro transcription. These long dsRNA molecules can be cut by Dicer or RNAseII into functional siRNAs. The final products are potent tools for the specific "knock-down" of genes, often superior to synthesized siRNA oligos.

About the RZPD:
RZPD - German Resource Center for Genome Research (Deutsches Ressourcenzentrum für Genomforschung) - is a non-for-profit service centre for genomics and proteomics research. Based on one of the largest clone collections worldwide, it provides high quality research material, high throughput technology and automation solutions for academic institutions as well as for industry. Material and services that are available from RZPD include clones of genomic and cDNA libraries, high density colony, DNA, and protein arrays, genomic and cDNA pools, non-redundant cDNA collections, pre-defined and custom microarrays, custom screening, expression profiling, Affymetrix service, robotic services, large scale PCR amplification, and cDNA library generation. Data produced with its material are integrated in RZPD's Primary Database and linked to additional data from public databases. That way, for the benefit of the researchers a multitude of data is linked to the clone material available at RZPD and multiplication of work is avoided. No intellectual property (IP) is claimed by RZPD for results derived from the use of its material. If in single cases IP is claimed by the originator of clone material provided to and distributed by RZPD, this is clearly stated and conditions are passed on by RZPD to the user.

Further information on the RZPD are available at www.rzpd.de or directly on the press pages http://www.rzpd.de/about/press/ .

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Contact:
RZPD - Deutsches Ressourcenzentrum für Genomforschung GmbH
Dr. Johannes Maurer - Scientific Managing Director
Heubnerweg 6
D-14059 Berlin, Germany
Tel.: +49-30-32639-251
Fax: +49-30-32639-262
eMail: j.maurer@rzpd.de 

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