The DNA molecule, which is the support of the genetic information, is continuously altered within cells by endogenous and exogenous processes. Among these reactions that alter the structure of the biopolymer, the hydrolytic reactions are the most common. The latter processes lead to loss or modification of the nucleic bases of DNA (the famous A, C, G and T letters). Thus a major alteration (estimated at thousands of lesions per human cell) formed by the cytosine hydrolysis is the Uracil lesion. The presence of the latter residue within DNA is highly mutagenic (by modification of the genetic message) and may initiate cancer processes. Researchers at INAC, in collaboration with colleagues from the Institut Gustave Roussy in Paris, the Academy of Sciences in Warsaw and the University of Novosibirsk, have recently discovered a new repair pathway able to efficiently eliminate this damage, by using the AP-endonuclease protein.
The contribution of researchers from INAC in the present work was dual: on the one hand in the preparation of the synthetic DNA fragments containing the lesion (by a total chemical synthesis) and secondly by the dissection of the molecular mechanism involved in the incision of the lesion by the repair protein. This new enzymatic process was identified through an original approach, developed at INAC, based on a MALDI-TOF mass spectrometry analysis using a laser ionization source. This analytical technique allowed here an univocal identification of DNA fragments released during the repair step by incision.
Works are currently in progress in our laboratory to extend this mass spectrometry-based approach to the characterization of new synthetic DNA fragments and structural analogs, as well as analysis of other enzymatic repair and replication processes.
Publication: P. Prorok , D. Alili, C. Saint-Pierre, D. Gasparutto, D.O. Zharkov, A.A. Ishchenko, B. Tudek, M.K. Saparbaev, PNAS (2013) vol. 110, pp. E3695-E3703 .
Maj : 06/03/2014 (1006)