Press Page Christian Biertümpfel

DNA Doctors

The DNA in our cells is constantly under attack: high-energy radiation, ultraviolet rays or toxic chemicals can damage and even break DNA. Because such defects can lead to serious diseases like cancer or cause birth defects, cells try to repair damage as soon as possible. Christian Biertümpfel and his research group want to elucidate these repair mechanisms.

T4 endonuclease VII unwinds a DNA knot

Particularly dangerous is a completely severed DNA molecule. Such a double strand break poses two risks at the same time: If the damage cannot be repaired, a cell is forced to destroy itself through “programmed cell suicide” (apoptosis). On the other hand, if the damage is repaired incorrectly, massive alterations can remain in the DNA. Biertümpfel is therefore interested in a specific cellular repair mechanism implemented in double-strand breaks that is generally error-free: homologous recombination.

Better safe than sorry
This kind of repair is made possible, because in higher organisms genetic information exists in duplicate. During homologous recombination the intact and damaged DNA strands are intertwined in a “molecular knot”, the so-called Holliday structure. Based on the undamaged safety copy, the defective DNA molecule can be repaired. Once the repair has been completed, the Holliday junction is resolved so that once again two functional DNA molecules exist.

Insight into a network
In a first step, Biertümpfel would like to investigate this critical and extremely complex cellular process. In the long term he and his team want to decipher the entire modular network of DNA repair as well as its regulation and cellular links – also in cases in which the mechanisms reach their limits.


The so-called Holliday structure has nothing to do with holidays or vacation, but is rather a term that describes a complex crossover of similar DNA strings. Researcher Robin Holliday proposed this… more