Regulation of MicroRNAs in Drosophila

Science's STKE  24 Jun 2003:
Vol. 2003, Issue 188, pp. tw242
DOI: 10.1126/stke.2003.188.tw242

MicroRNAs (miRNAs) are produced during development and play a key role in controlling the timing of developmental transitions. These miRNAs are produced from longer precursor RNAs and act as gene repressors, by blocking translation. Two groups analyzed regulation of miRNAs in Drosophila and arrived at different conclusions. Bashirullah et al. and Sempere et al. both noted that let-7 and miR-125 expression was stimulated at the onset of pupariation. However, Sempere et al. concluded that the hormone ecdysone was essential for this induction of expression based on analysis of expression in ecd mutants (that are deficient in the synthesis of ecdysone) and in npr mutants (that are deficient in the broad complex transcription factor, a mediator of ecdysone signaling). Bashirullah et al. concluded that ecdysone was not controlling the expression of let-7 and miR-125, because in flies treated with interfering RNA against the ecdysone receptor, expression of these two miRNAs was still stimulated during puparium formation. Both groups observed ecdysone stimulation of expression of let-7 and miR-125 in cultured cells; however, stimulation required prolonged exposure that did not correlate to the pulse of ecdysone that occurs in vivo. Furthermore, ecdysone did not stimulate expression of let-7 or miR-125 in organ cultures. Both groups did mention the clustering of these miRNA genes and their coordinate regulation as a consequence of their chromosomal proximity. Although some results were in common between the two groups, the regulation of the production of the miRNAs in flies remains a controversial issue.

A. Bashirullah, A. E. Pasquinelli, A. A. Kiger, N. Perrimon, G. Ruvkun, C. S. Thummel, Coordinate regulation of small temporal RNAs at the onset of Drosophila metamorphosis. Dev. Biol. 259, 1-8 (2003). [Online Journal]

L. F. Sempere, N. S. Sokol, E. B. Dubrovsky, E. M. Berger, V. Ambros, Temporal regulation of microRNA expression in Drosophila melanogaster mediated by hormonal signals and Broad-Complex gene activity. Dev. Biol. 259, 9-18 (2003). [Online Journal]