Main Field(s) of Research, Abstract
Background: The maintenance of genetic stability is of crucial importance for any form of life. Prior to cell division in each mammalian cell, the process of DNA replication must faithfully duplicate the three billion bases with an absolute minimum of mistakes. On the other hand DNA itself is highly reactive and is constantly attacked by endogenous factors and is also easily altered by intracellular processes such as oxidation. It was estimated that a mammalian genome undergoes about 100,000 modifications per day. Powerful repair mechanisms must therefore exist to restore the bona fide DNA structure and sequence. Surveillance of the genome is accomplished by various DNA repair mechanisms, which have evolved to remove or to tolerate all kind of DNA lesions in a generally error-free way.
Working hypothesis: It is likely that the compomponts of the DNA replication apparatus, DNA repair components of certain pathways such as e.g. non-homologus end joining (NHEJ) and base excision repair (BER) can interact in case of genotoxic stress situations with checkpoint sensor proteins such as Rad 1, Rad 9, Hus 1 and Rad17.
Specific aims: This grant application contains two subprojects: First, efforts are made to identify the in vivo role of DNA polymerase lambda and its ancestor in the extremely radioresistent bacterium Deinococcus radiodurans. Second, by using the in vitro long patch base excision repair (LP-BER) with purified components and the checkpoint clamp and clamp loader we want to learn more about the LP-BER pathway and how it can interact with proteins sensing DNA damages.
Experimental design: Both projects are approached by the dual methods of in vitro and in vivo. Interaction will be tested under physiological and genotoxic stess conditions. Both projects use the standard biochemical and molceluar biological test methods for the characterization of inteacting proteins and for enzymatic testing. The in vivo approach in Project 1 is a collaboration with Prof. Susanne Sommer’s lab in Paris who is qualified to work with the extremely high doses of x-rays. The Project 2 includes for the in vivo work cell culture technologies that are available at the Institute of Veterinary Biochemistry and Molecular Biology.
Expected value of proposed project: The radioresistant bacterium Deinococcus radiodurans might give us insight into the repair event of double-strand breaks, a knowledge that can be adapted subsequently in human cells as well. The LP-BER experiments will tell us how cells react under genotoxic stress conditions to avoid or at least to minimize alterations of the DNA. The exact mechanistic knowledge how “problems and damages” on the DNA are dealt within a cell is of paramount interest to understand the initial of events of genetic instability that eventually leads to a cancerous phenotype or to cell death (e.g. apoptosis).

Main Fields of Research, Keywords
DNA replication and DNA repair mechanisms in mammalian cells (animal and human), DNA repair mechanisms in the radioresistant organism Deinococcus radiodurans, DNA polymerase from the X family, flap endonuclease 1, DNA ligase I

Special Techniques and Equipment
All relevant techniques to carry out biochemistry, molecular- and and cell biology

Education and Training
We have training opportunities for PhD students (MNF and Veterinary Medicine), PostDocs and Veterinary Medical thesis.