Identification of cellular targets of viral miRNAs

Coordinator:		Dr. Gunter Meister
Institution:		Max-Planck-Institut für Biochemie, Martinsried
Homepage:		www.biochem.mpg.de/en/rg/meister/

Many cellular miRNAs are expressed in distinct tissues or developmental stages. Moreover, miRNAs play important roles in diseases including different forms of cancer such as B-cell lymphomas or colorectal cancer, or virus infections. In many forms of cancer, miRNA expression is mis-regulated and it has therefore been proposed that miRNAs might have a role in tumor biology. In viral infections, both viral and cellular miRNAs are important for infection and virus production. However, only very little is known about the functional details of such miRNAs and the mRNAs, which they regulate.
Bio-informatic predictions based on sequence conservation and free binding energy between the miRNA and a target mRNA have been reported. On average, different algorithms predict about 150 to 200 target mRNA per miRNA and therefore it has been suggested that about 30% of all human genes are under the control of miRNAs. However, the main shortcoming of computer approaches is that targets are predicted on a genome-wide scale and it is very difficult to find targets that are specific to tissues or developmental stages. Therefore, only a few miRNA targets have been experimentally validated thus far and it is very important to develop biochemical strategies to directly identify mRNAs that are regulated by miRNAs.
The goal of the proposed project is to use biochemical tools to identify cellular but also viral RNAs that are regulated by miRNAs. We have demonstrated that miRNAs form stable complexes with Ago proteins as well as target mRNAs, which can be efficiently purified using antibodies against Ago proteins.
In close collaboration with Prof. Friedrich Grässer (Homburg/Saar, Partner 4) we will identify miRNA targets from EBV-positive and EBV-negative cells. Purified mRNAs will be identified in collaboration with Prof. Jürgen Haas (Munich, Partner 1) using affimetrix technology and the data will be analyzed in collaboration with Prof. Zimmer (Munich, Partner 7). At later stages we will extend our studies to other herpesvirus-family members in collaboration with other partners of the IG. Our analysis will therefore provide a miRNA target platform of which all members of the proposed IG will benefit.
We hope that our studies not only contibute to a better understanding of Herpes-Virus infection but may also help to find new strategies for therapy.