DNA Methylation Effects in Friedreich Ataxia (FRDA)
The sulfur-iron cluster serves as the universal coordinator of the delivery of both iron and sulfur. The most of the authors (Ding B., Smith amp. Ding T., 2005) consider that sulfur in iron-sulphur clusters is derived from L-cysteine and can participate in the numerous biochemical processes, e.g. oxidation-reduction reactions, acid cycle (TCA), nitrogen fixation, amino acid biosynthesis, hem and biotin biosynthesis, DNA synthesis and repair, and regulation of gene expression, etc as one of the principal contributor of the processes of electron transferring. There is known (ibid) also that sulfur-iron clusters work as the modulators and can create complexes with proteins. They also can act as the catalytic centers and sensors of iron and oxygen. The control of iron level in the intracellular structure is the crucial for the normal functioning of cellular organelles because the intracellular ‘free’ iron concentration is tightly controlled, because the elevated levels of the plenty of ‘free’ iron may activate the peroxidative processes and, particularly, the production of hydroxyl free radicals and peroxidation oxidization of lipids.. There was demonstrated that the clinical symptoms of Friedreich ataxia are associated with the progressive neurodegeneration in the posterior columns of medulla spinalis and a clear correlation exists between the size of the repeating expansion of GAA triplet and severity of the phenotypic manifestations of Friedreich ataxia (Alper amp. Naraynan, 2003. McDaniel et al., 2001). However, some patients can have normal levels of frataxin (Kimura et al., 2002. van der Warrensburg, Knoers amp. Kremer, 2002), a phenomenon, which current studies cannot explain as yet.