Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The recently discovered microRNAs (miRNAs) are a large family of small regulatory RNAs that have been implicated in controlling diverse pathways in a variety of organisms (1, 2). For posttranscriptional gene silencing, one strand of the miRNA is used to guide components of the RNA interference machinery, including Argonaute 2, to messenger RNAs (mRNAs) with complementary sequences (3, 4). Thus, targeted mRNAs are either cleaved by the endonuclease Argonaute 2 (5, 6), or protein synthesis is blocked by an as yet uncharacterized mechanism (7, 8). Genes encoding miRNAs are transcribed as long primary miRNAs (pri-miRNAs) that are sequentially processed by components of the nucleus and cytoplasm to yield a mature, approx 22-nucleotide (nt)-long miRNA (9). Two members of the ribonuclease (RNase) III endonuclease protein family, Drosha and Dicer, have been implicated in this two-step processing (10-13). To further our understanding of miRNA biogenesis and function it will be essential to identify the protein complexes involved. We were interested in defining the proteins required for the initial nuclear processing of pri-miRNAs to the approx 60- to 70-nt stem-loop intermediates known as precursor miRNAs (pre-miRNAs) (9, 10). This led to our identification of a protein complex we termed Microprocessor, which is necessary and sufficient for processing pri-miRNA to premiRNAs (14). The Microprocessor complex comprises Drosha and the double-stranded RNAbinding protein DiGeorge syndrome critical region 8 gene (DGCR8), which is deleted in DiGeorge syndrome (15, 16). In this chapter, we detail the methods used for the biochemical isolation and identification of the Microprocessor complex from human cells. We include a protocol for the in vitro analysis of pri-miRNA processing activity of the purified Microprocessor complex.
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PMID:MicroRNA biogenesis: isolation and characterization of the microprocessor complex. 1695 65

MicroRNA (miRNA) genes are transcribed into long primary transcripts (pri-miRNAs) that get processed into mature miRNAs of about 22 nt in length by two different ribonuclease (RNase) III enzymes, Drosha and Dicer. Various experimental protocols have been developed and modified for genetic and biochemical analyses for microRNA processing. Here we describe the methods for the analysis of pri-miRNA processing that is mediated by Drosha and its cofactor, DiGeorge Syndrome Critical Region Gene 8 (DGCR8).
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PMID:In vitro and in vivo assays for the activity of Drosha complex. 1772 Apr 80

In animals, the Microprocessor complex cleaves primary transcripts of microRNAs (pri-miRNAs) to produce precursor microRNAs in the nucleus. The core components of Microprocessor include the Drosha ribonuclease and its RNA-binding partner protein DiGeorge critical region 8 (DGCR8). DGCR8 has been shown to tightly bind an Fe(III) heme cofactor, which activates its pri-miRNA processing activity. Here we describe how to reconstitute pri-miRNA processing using recombinant human Drosha and DGCR8 proteins. In particular, we present the procedures for expressing and purifying DGCR8 as an Fe(III) heme-bound dimer, the most active form of this protein, and for estimating its heme content.
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PMID:Primary microRNA processing assay reconstituted using recombinant Drosha and DGCR8. 2416 3

The RNA-binding heme protein DiGeorge critical region 8 (DGCR8) and its ribonuclease partner Drosha cleave primary transcripts of microRNA (pri-miRNA) as part of the canonical microRNA (miRNA) processing pathway. Previous studies show that bis-cysteine thiolate-coordinated Fe(III) DGCR8 supports pri-miRNA processing activity, while Fe(II) DGCR8 does not. In this study, we further characterized Fe(II) DGCR8 and tested whether CO or NO might bind and restore pri-miRNA processing activity to the reduced protein. Fe(II) DGCR8 RNA-binding heme domain (Rhed) undergoes a pH-dependent transition from 6-coordinate to 5-coordinate, due to protonation and loss of a lysine ligand; the ligand bound throughout the pH change is a histidine. Fe(II) Rhed binds CO and NO from 6- and 5-coordinate states, forming common CO and NO adducts at all pHs. Fe(II)-CO Rhed is 6-coordinate, low-spin, and pH insensitive with the histidine ligand retained, suggesting that the protonatable lysine ligand has been replaced by CO. Fe(II)-NO Rhed is 5-coordinate and pH insensitive. Fe(II)-NO also forms slowly upon reaction of Fe(III) Rhed with excess NO via a stepwise process. Heme reduction by NO is rate-limiting, and the rate would be negligible at physiological NO concentrations. Importantly, in vitro pri-miRNA processing assays show that both CO- and NO-bound DGCR8 species are inactive. Fe(II), Fe(II)-CO, and Fe(II)-NO Rhed do not bear either of the cysteine ligands found in the Fe(III) state. These data support a model in which the bis-cysteine thiolate ligand environment of Fe(III) DGCR8 is necessary for establishing proper pri-miRNA binding and enabling processing activity.
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PMID:CO and NO bind to Fe(II) DiGeorge critical region 8 heme but do not restore primary microRNA processing activity. 2776 92