Post-transcriptional control of DGCR8 expression by the Microprocessor

Abstract

The Microprocessor, comprising the RNase III Drosha and the double-stranded RNA binding protein DGCR8, is essential for microRNA (miRNA) biogenesis. In the miRNA processing pathway certain hairpin structures within primary miRNA (primiRNA) transcripts are specifically cleaved by the Microprocessor to release ;60-70-nucleotide precursor miRNA (premiRNA) intermediates. Although both Drosha and DGCR8 are required for Microprocessor activity, the mechanisms regulating the expression of these proteins are unknown. Here we report that the Microprocessor negatively regulates DGCR8 expression. Using in vitro reconstitution and in vivo studies, we demonstrate that a hairpin, localized in the 59 untranslated region (59UTR) of DGCR8 mRNA, is cleaved by the Microprocessor. Accordingly, knockdown of Drosha leads to an increase in DGCR8 mRNA and protein levels in cells. Furthermore, we found that the DGCR8 59UTR confers Microprocessor-dependent repression of a luciferase reporter gene in vivo. Our results uncover a novel feedback loop that regulates DGCR8 levels.

Processing of microRNA primary transcripts requires heme in mammalian cells

“…Overall, our results seem to suggest that, in HeLa cells, DGCR8, not Drosha, is the rate-limiting factor for pri-miRNA processing. This notion is consistent with the previous reports that the DGCR8 protein is subjected to multiple layers of regulation (5,30,(33)(34)(35)(36).…”

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

“…It should also be noted that the microprocessor is able to target and cleave the DGCR8 mRNA (Han et al, 2009;Kadener et al, 2009;Triboulet et al, 2009). Although targeting of other mRNAs by the microprocessor (Kadener et al, 2009) is still controversial (Shenoy and Blelloch, 2009), we cannot exclude that inhibiting Drosha or DGCR8 could modify the expression of non-pri-miRNA RNAs.…”

Structure of the dimerization domain of DiGeorge Critical Region 8

“…Second, recent studies show that the stability of DGCR8 messenger RNA is regulated through cleavage of its pri-miRNA-like hairpin structures by the Microprocessor complex. [33][34][35] Thus, DGCR8-heme association may be part of the homeostatic control of miRNA biogenesis. Finally, signals that modulate DGCR8 activity likely work in combination with other mechanisms to control the expression and activity of miRNAs.…”