Identificação e caracterização de microRNAs no fungo dimórfico Histoplasma capsulatum

Abstract

MicroRNAs are small non-coding RNA molecules involved in the RNA interference phenomenon. These small RNAs contain between 18 and 25 nucleotides and are derived from precursors containing a hairpin structure. Their biogenesis and mode of action are well understood in plants and animals, but in fungi their biogenesis is still poorly understood. However, small RNAs similar to microRNAs (miRNAs-like) have been identified in various fungi, such as Neurospora crassa, Sclerotinia sclerotiorum, Penicillium marneffei, Trichoderma reesei and Paracoccidioides brasiliensis. Even though the amount of data on these molecules in the Fungi kingdom has been increasing, up to now there are no descriptions of microRNAs in important human pathogens such as Histoplasma capsulatum. Therefore, due to the absence of the characterization of this regulatory mechanism in this human pathogen, this study aimed to identify microRNAs in this pathogen and to infer the biological processes regulated by these interference RNAs in this fungus. In order to do so, the methodology employed in this study was the search for published microRNAs sequences for other fungi in the literature and in silico analysis to predict the homology of these known sequences to genome regions of two H. capsulaum strains H88 and G217B. After the bioinformatics analysis, we identified six microRNAs in H. capsulatum H88 and four microRNAs in H. capsulatum G217B .One of the microRNAs was conserved in both strains. This microRNA was selected for target investigation. We identified 551 targets in the H88 strain and 495 targets in the G217B strain. Biological processes identified as being regulated by this microRNA comprise the synthesis and the degradation of cell wall components, the energetic metabolism and DNA processing. The results imply the presence of microRNAs in this fungi and a high number of targets for each microRNA, which hints on the existence of a complex network of microRNA post-transcriptional regulation in H. capsulatum.