Análise da expressão gênica em Trypanosoma cruzi em resposta à radiação ionizante pela técnica de microarranjo de DNA

Abstract

Among the various types of damages caused by ionizing radiation, the lesions of greatest biological importance are the double-stranded DNA breaks. The tolerance for this type of damage requires an efficient apparatus for recognition and repair of lesions and these characteristics define the degree of resistance of various organisms to this type of stress. Trypanosoma cruzi is highly resistant to gamma rays, considering that a 500 Gy dose induces a genomic DNA fragmentation, but the karyotype is gradually repaired and the chromosomal bands pattern is restored in less than 48 hours. In this study, we aimed to compare T. cruzi epimastigotes gene expression from two biological replicates irradiated or not with a sub-lethal dose of 500 Gy, through microarray experiments. Our results showed that irradiation caused an arrest in cell growth, but did not significantly affect the integrity of RNA molecules, contrary to what was seen in DNA molecules. The gene expression was affected in a time-dependent manner, because the peak of down-regulated genes (composed mostly of genes with known function) and up-regulated genes (composed mostly of genes of unknown function) occurred after 4 and 96 hours, respectively. Four maxicircle genes and those coding for retrotransposons hot spot protein (RHSs) were strongly induced after 48 hours. However, genes related to basal metabolic functions presented a decrease in the expression levels. There was no induction in the expression of DNA repair genes, excepted for the tyrosil-DNA phosphodiesterase 1 gene.