Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009 Jan 9;136(1):75-84.
doi: 10.1016/j.cell.2008.10.053.

Posttranscriptional crossregulation between Drosha and DGCR8

Jinju Han  1 , Jakob S Pedersen, S Chul Kwon, Cassandra D Belair, Young-Kook Kim, Kyu-Hyeon Yeom, Woo-Young Yang, David Haussler, Robert Blelloch, V Narry Kim
Affiliations

Posttranscriptional crossregulation between Drosha and DGCR8

Jinju Han et al. Cell. .

Abstract

The Drosha-DGCR8 complex, also known as Microprocessor, is essential for microRNA (miRNA) maturation. Drosha functions as the catalytic subunit, while DGCR8 (also known as Pasha) recognizes the RNA substrate. Although the action mechanism of this complex has been intensively studied, it remains unclear how Drosha and DGCR8 are regulated and if these proteins have any additional role(s) apart from miRNA processing. Here, we report that Drosha and DGCR8 regulate each other posttranscriptionally. The Drosha-DGCR8 complex cleaves the hairpin structures embedded in the DGCR8 mRNA and thereby destabilizes the mRNA. We further find that DGCR8 stabilizes the Drosha protein via protein-protein interaction. This crossregulation between Drosha and DGCR8 may contribute to the homeostatic control of miRNA biogenesis. Furthermore, microarray analyses suggest that a number of mRNAs may be downregulated in a Microprocessor-dependent, miRNA-independent manner. Our study reveals a previously unsuspected function of Microprocessor in mRNA stability control.

PubMed Disclaimer

Figures

Figure 1
Figure 1. Drosha Downregulates DGCR8 mRNA and Protein Expression at the Posttranscriptional Level
(A) Quantitative real-time PCR (qRT-PCR) after Drosha depletion. Total RNA was prepared from HeLa cells 72 hr after transfection of siRNA against Drosha (siDrosha). siRNA against GFP (siGFP) was used as a control. Three biologically independent experiments were performed for quantification (mean ±SD). (B) Western blot analysis after knockdown. HeLa cell extract was prepared 72 hr after siRNA transfection. The p27, a target of miR-221/222, is used as a control. Quantitative results are shown in the right panel. Three independent experiments were performed for quantification (mean ±SD). (C) RT-PCR and western blot analysis after overexpression of the transdominant negative (TN) Drosha mutant in HEK293T cells. Drosha (TN) is a mutant lacking the catalytic activity. Wild-type (WT) Drosha was used as a control. Though the juxtaposed lanes are not contiguous, all of them are from a single gel, which is true for all the membranes with dashed lines. The primer set, Ex1-Ex2, amplifies endogenous DGCR8 mRNA. (D) Nuclear runoff assay after Drosha depletion. The nuclei of miR-30a-inducible HeLa cells were prepared after siRNA transfection and doxycycline treatment. For quantification of the nuclear runoff, the band intensity was determined by phosphoimager and normalized against β-actin levels. Two independent experiments were performed for quantification (mean ±SD). (E) Turnover rate of DGCR8 mRNA in Drosha-depleted cells. Actinomycin D (ActD) (5 μg/ml) was added to HEK293T cells 40 hr after siRNA transfection. Total RNAs are prepared at the indicated point after ActD treatment. The band intensity from northern blot was measured by Multi Gauge program(Fuji) and normalized against GAPDH mRNA. The relative DGCR8 mRNA levels were determined from three independent experiments (mean ±SD). A representative data is shown in Figure S3A. (F) RT-PCR analysis of DGCR8 mRNA in subcellular fractions after RNAi in HEK293T cells. The exon and intron of GAPDH were amplified as markers of cytoplasmic RNA and nuclear RNA, respectively.
Figure 2
Figure 2. The Hairpins in DGCR8 mRNA Are Cleaved by Drosha In Vitro
(A) Partial sequences of DGCR8 mRNA of human, mouse, rat, chicken, and zebrafish. There are two hairpin structures, hairpin A in the 5′ UTR and hairpin B in the coding region. A black bar presents a template for in vitro transcription. This figure is adapted from Pedersen et al. (2006). (B) In vitro processing of the DGCR8 hairpins. Internally labeled hairpins were incubated with total cell extract (TCE) or FLAG-immunopurified (FLAG-IP) Drosha. Cleavage fragments are marked by red or blue triangles. (C) In vitro processing of the DGCR8 hairpins with a Drosha mutant E110aQ. Pri-miR-16-1 was used as a control. (D) Cleavage site mapping of the two hairpins. The cleavage sites are indicated with triangles. The color of the triangles shows the origin of the fragments presented in Figure 2B. Size of the triangle reflects the clone frequency such that the frequencies of 99%-75%, 74%-50%, and 49%-25% are shown with large, medium, and small triangles, respectively. The cleavage sites with clone frequencies of under 25% are not presented in this figure. Gray lines under the hairpins represent the binding sites for the probes used for northern blotting.
Figure 3
Figure 3. Conservation of the Regulation of DGCR8
(A) RT-PCR and western blot analysis after mouse Drosha and mouse DGCR8 depletion. Total RNA and cell extract of NIH 3T3 cells were prepared 72 hr siRNA transfection. (B) RT-PCR analysis after Drosha knockdown in D. melanogaster S2 cells. Total RNA of S2 cells was prepared 7 days after addition of long doublestranded RNAs that target fly Drosha (dsDrosha). Reverse transcription was carried out with random primer. Pri-Bantam was amplified as a positive control.
Figure 4
Figure 4. Drosha Cleaves the DGCR8 mRNA In Vivo
(A) Northern blot assay to detect the cleavage fragments from the hairpin A in HEK293T cells. Probe is complementary to the 5′ stem region of hairpin A marked as a gray underline in Figure 2D. Small RNAs under 200 nt were enriched after siRNA transfection. As a loading control, tRNA was probed. Protein knockdown was confirmed by western blotting. (B) Northern blot assay. Total RNAs were prepared from HEK293T cells transfected with either empty vector or the plasmid expressing both hairpins. (C) Northern blot assay. HEK293T cells were fractionated into nucleus and cytoplasm. The RNAs were extracted from each fraction, dissolved in the same amount of TE, and loaded on the gel. Fractionation efficiency is confirmed by measurement of GAPDH mRNA and pri-miR-21 as the cytoplasmic and nuclear markers, respectively.
Figure 5
Figure 5. Drosha Is Positively Controlled by DGCR8 through Protein-Protein Interaction
(A) Western blot analysis of the transiently expressed Drosha protein. In HEK293T cells, Drosha-FLAG was transiently transfected with FLAG null vector or DGCR8-FLAG. (B) Western blot analysis of endogenous Drosha protein after overexpression of DGCR8. V5-tagged DGCR8 was transiently expressed in HeLa cells. (C) Western blot analysis after transient expression of various DGCR8 mutants. The Drosha-FLAG and V5-DGCR8 mutants were coexpressed in HEK293T cells. Though the juxtaposed lanes are not contiguous, all of them are from a single gel, which is true for all the membranes with dashed lines. DGCR8 mutants were schematized and their Drosha binding abilities are presented on the right.
Figure 6
Figure 6. Expression of Drosha and DGCR8 in Dgcr8 KO Mouse ES Cells
(A) Western blot analysis of Drosha in mouse ES cells. Δ/flox indicates heterozygote cells, and Δ/Δ indicates homozygous null cells. Two different KO lines (c1 and c2) were used for the experiments (lanes 3 and 4). The Dicer KO ES line (dicer Δ/Δ) was used as a control (Babiarz et al., 2008). (B) Quantitation of the Drosha mRNA by Affymetrix chip analysis. Three independent experiments were performed (mean ±SD). The methods are described in Wang et al. (2008b). (C) Western blot analysis of DGCR8 in mouse ES cells. The asterisk represents a nonspecific band which serves as a loading control. (D) Quantitative real time PCR (qRT-PCR) of the DGCR8 mRNA in Dgcr8 KO mES cell. The relative DGCR8 mRNA levels were determined in wild-type (flox/flox) and heterozygote (Δ/flox). Three independent experiments were performed for quantification (mean ±SD).
Figure 7
Figure 7. Model for the Crossregulation between Drosha and DGCR8
The Drosha protein cleaves the hairpins on the DGCR8 mRNA and destabilizes the mRNA, while the DGCR8 protein positively regulates the Drosha protein via protein-protein interaction. Drosha may be involved in the stability control of other mRNAs.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Ambros V, Bartel B, Bartel DP, Burge CB, Carrington JC, Chen X, Dreyfuss G, Eddy SR, Griffiths-Jones S, Marshall M, et al. A uniform system for microRNA annotation. RNA. 2003;9:277–279. - PMC - PubMed
    1. Babiarz JE, Ruby JG, Wang Y, Bartel DP, Blelloch R. Mouse ES cells express endogenous shRNAs, siRNAs, and other Microprocessor-independent, Dicer-dependent small RNAs. Genes Dev. 2008;22:2773–2785. - PMC - PubMed
    1. Bushati N, Cohen SM. microRNA functions. Annu. Rev. Cell Dev. Biol. 2007;23:175–205. - PubMed
    1. Denli AM, Tops BB, Plasterk RH, Ketting RF, Hannon GJ. Processing of primary microRNAs by the Microprocessor complex. Nature. 2004;432:231–235. - PubMed
    1. Elbashir SM, Lendeckel W, Tuschl T. RNA interference is mediated by 21- and 22-nucleotide RNAs. Genes Dev. 2001;15:188–200. - PMC - PubMed

Publication types