Comprehensive analysis of mammalian miRNA* species and their role in myeloid cells

The locus of microRNA-10b

“…However, different groups very recently demonstrated that the biological relevance of microRNAs* may be comparable to that of the guide strand, and that deregulation of their expression could be strictly linked to cancer insurgence and development. [24][25][26] The star strand of the miR-10b locus, miR-10b*, was first functionally characterized by our group in a recent report, 27 in which we also showed that it is downregulated in primary breast tumors when compared with peritumoral noncancerous surrounding tissues. This feature is common to all the analyzed breast cancer subtypes, suggesting that miR-10b* downregulation represents an early event in breast tumorigenesis.…”

Identification of microprocessor-dependent cancer cells allows screening for growth-sustaining micro-RNAs

“…We therefore note that, although this hypothesis has still to be tested, our data could also be explained by functional expression of miR-27b*. Indeed, (i) the miR expression system that we used is designed to lead to expression of the natural premiRNA, including the miR* part; (ii) miR-27b* and miR-27a* differ by several nucleotides, including one point mutation in the seed and (iii) miR-27b* is actually expressed in vivo, as shown by miR-27b/miR-27b* ratios of around 10 (Kuchenbauer et al, 2011). On the other hand, we also detected a series of specificities that differentiated the ES cell-based screen from our data: (i) ES cell-expressed micro-RNAs (miR-302, miR-372/3) were found to rescue CoGAM less efficiently than miR-19 and miR-20, a difference that was not detected by complementation of DGCR8 knockout in ES cells; (ii) the rescuing effects of miR-19b and miR-27b appeared specific for CoGAM and (iii) p21, which participates in the growth inhibition observed in DGCR8 ko ES cells, is not involved in CoGAM.…”

Passenger strand loading in overexpression experiments using microRNA mimics

“…For many miRNAs only one of the strands is preferentially selected as guide (either 5p or 3p), while for others both strands are used equally. 1 Various strategies have been adopted to manipulate miRNA levels for functional studies. Overexpression in cell culture can be achieved with vectors expressing the natural miRNA gene or a short hairpin, but the combined effects of 5p and 3p miRNAs may complicate interpretation of the results when both are functional.…”