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A nodal regulator of endoplasmic reticulum stress is the transcription factor, ATF6, which is activated by ischemia and protects the heart from ischemic damage, in vivo. To explore mechanisms of ATF6-mediated protection in the heart, a whole-genome microRNA (miRNA) array analysis of RNA from the hearts of ATF6 transgenic (TG) mice was performed. The array identified 13 ATF6-regulated miRNAs, eight of which were downregulated, suggesting that they could contribute to increasing levels of their mRNAs. The down-regulated miRNAs, including miR-455, were predicted to target 45 mRNAs that we had previously shown by microarray analysis to be up-regulated by ATF6 in the heart. One of the miR-455 targets was calreticulin (Calr), which is up-regulated in the pathologic heart, where it modulates hypertrophic growth, potentially reducing the impact of the pathology. To validate the effects of miR-455, we showed that Calr protein was increased by ATF6 in mouse hearts, in vivo. In cultured cardiac myocytes, treatment with the ER stressor, tunicamycin, or with adenovirus encoding activated ATF6 decreased miR-455 and increased Calr levels, consistent with the effects of ATF6 on miR-455 and Calr, in vivo. Moreover, transfection of cultured cardiac myocytes with a synthetic precursor, premiR-455, decreased Calr levels, while transfection with an antisense, antimiR-455, increased Calr levels. The results of this study suggest that ER stress can regulate gene expression via ATF6-mediated changes in micro-RNA levels. Moreover, these findings support the hypothesis that ATF6-mediated down-regulation of miR-455 augments Calr expression, which may contribute to the protective effects of ATF6 in the heart.
Pubmed ID: 22326432
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Central online repository for microRNA nomenclature, sequence data, annotation and target prediction.Collection of published miRNA sequences and annotation.
View all literature mentionsDatabase of microRNA target predictions and expression profiles. Target predictions are based on a development of the miRanda algorithm which incorporates current biological knowledge on target rules and on the use of an up-to-date compendium of mammalian microRNAs. MicroRNA expression profiles are derived from a comprehensive sequencing project of a large set of mammalian tissues and cell lines of normal and disease origin. This website enables users to explore: * The set of genes that are potentially regulated by a particular microRNA. * The implied cooperativity of multiple microRNAs on a particular mRNA. * MicroRNA expression profiles in various mammalian tissues. The web resource provides users with functional information about the growing number of microRNAs and their interaction with target genes in many species and facilitates novel discoveries in microRNA gene regulation. The microRNA Target Detection Software, miRanda, is an algorithm for finding genomic targets for microRNAs. This algorithm has been written in C and is available as an open-source method under the GPL.
View all literature mentionsWeb tool to predict biological targets of miRNAs by searching for presence of conserved 8mer, 7mer and 6mer sites that match seed region of each miRNA. Nonconserved sites are also predicted and sites with mismatches in seed region that are compensated by conserved 3' pairing. Used to search for predicted microRNA targets in mammals.
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