CONICET | Buscador de Institutos y Recursos Humanos

MicroRNAs (miRNAs) are a class of regulatory RNAs of ~21 nucleotides that post-transcriptionallyregulate eukaryotic gene expression by directing mRNA cleavage or inhibiting translation. They areinvolved in diverse physiological processes like development, differentiation and metabolism.The miRNA miR398 regulates Cu/Zn superoxide dismutases (CSD1 and CSD2) that detoxifysuperoxide radicals; and a subunit of Cytochrome C Oxidase, COX5b1. All these proteins bind Cuas a cofactor.Copper deficiency in the growth media induces miR398, which in turn guides the degradation of itstargets. As a consequence, the available copper is directed to essential proteins. It has beenobserved that miR398 exhibits differential activity towards its targets, being CSD1 and CSD2 moresensitive than COX5b1 to the miRNA levels.Interestingly, each gene regulated by miR398 has a specific nucleotide sequence at the target sitethat has been conserved during evolution. One possibility is that these differences in the targetsites underlie the differential activity of miR398 towards its targets.To elucidate this point we prepared several variants of CSD2 and COX5b1 with specific mutationsat the target site and expressed them fused to GFP under the control of the constitutive promoter35S. Then, we analyzed the expression levels of each transgene under different Cu conditions.These experiments allowed us to compare the sensitivity of the different target sites to miR398. Amodel showing the relative importance of the target site sequence on miR398 activity will bepresented.