[SCAN] The role of Base Excision Repair (BER) for extreme radiation and desiccation resistance of Deinococcus radiodurans

Scan Seminar

Title: The role of Base Excision Repair (BER) for extreme radiation and desiccation resistance of Deinococcus radiodurans – report from a Marie Curie fellowship

Speaker: Elin Moe

From: Structural Genomics Laboratory, ITQB

Abstract:

Deinococcus radiodurans is a pigmented pink/orange bacterium which was first identified in 1956 in canned meat sterilised by ionising radiation. It stains as a Gram-positive bacterium, however the cell wall differs from other Gram-positive bacteria with respect to lipid composition and layers. D. radiodurans exhibits an outstanding resistance to ionising radiation and desiccation and tolerates radiation doses up to 5,000 Grays (Gy) without loss of viability whereas most other organisms cannot survive doses above 50 Gy. In order to analyse the role of the DNA repair machinery for this unusual phenotype, structural biology studies of proteins from three major DNA repair pathways have been initiated; Base Excision Repair (BER), Nucleotide Excision Repair (NER) and Recombination Repair (RR). I have focused on the BER pathway, while my collaborators in France have been working on the NER and RR pathways. The BER pathway in D. radiodurans contains an unusual high number of DNA glycosylases compared to other bacteria and the hypothesis for this project was that the BER pathway has a more dominant role for the radiation and desiccation resistance of this organism than previously believed. In order to test this hypothesis I was planning to perform gene expression profiling analysis of native strains and of BER knock out strains (oxidation repair proteins) upon exposure to genotoxic stress. I was also planning to analyse the importance of metal clusters for DNA damage recognition and repair by Electron Paramagnetic Resonance (EPR) and X-ray crystallography. In this seminar I will present our results from the metal cluster analysis and X-ray crystallography of the bifunctional DNA glycosylase Endonuclease III.