ATCG nucleotide fluctuation of Deinococcus radiodurans radiation genes

摘要

The radiation resistance-repair genes in Deinococcus radiodurans (DR) and E-coli were analyzed in terms of the A, T, C, G nucleotide fluctuations The studied genes were Rec-A, Rec-Q, and the unique DR PprA gene In an ATCG sequence, each base was assigned a number equal to its atomic number The resulting numerical sequence was the basis of the statistical analysis Fractal analysis using the Higuchi method gave a fractal dimension increase of the Deinococcus radiodurans genes as compared to E-coli, which is comparable to the enhancement observed in the human HARl region (HAR1F gene) over that of the chimpanzee Near neighbor fluctuation was also studied via the Black-Scholes model where the increment sequence was treated as a random walk series The Deinococcus radiodurans radiation gene standard deviations were consistently higher than that of the E-coli deviations, and agree with the fractal analysis results, The sequence stacking interaction was studied using the published nucleotide-pair melting free energy values and Deinococcus radiodurans radiation genes were shown to possess larger negative free energies The high sensitivity of the fractal dimension as a biomarker was tested with correlation analysis of the gamma ray dose versus fractal dimension and the R square values were found to be above 0.9 (N=5). When compared with other nucleotide sequences such as the rRNA sequences, HARl and its chimpanzee counterpart, the higher fluctuation (correlated randomness) and larger negative free energy of a DR radiation gene suggested that a radiation resistance-repair sequence exhibited higher complexity. As the HARl nucleotide sequence complexity and its transcription activity of co-expressing cortex protein reelin supported a positive selection event in humans, a similar inference of positive selection of coding genes could be drawn for Deinococcus radiodurans when compared to E-coli. The origin of such a positive selection would be consistent with that of a Martian environment.