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miRNA biogenesis in plants differs from animal biogenesis mainly in the steps of nuclear processing and export. Instead of being cleaved by two different enzymes, once inside and once outside the nucleus, both cleavages of the plant miRNA are performed by a Dicer homolog, called Dicer-like1 (DL1). DL1 is expressed only in the nucleus of plant ...
These two proteins homeostatically control miRNA biogenesis by an auto-feedback loop. [16] A 2nt 3' overhang is generated by Drosha in the nucleus recognized by Dicer in the cytoplasm, which couples the upstream and downstream processing events. Pre-miRNA is then further processed by the RNase Dicer into mature miRNAs in the cell cytoplasm.
The microprocessor complex consists minimally of two proteins: Drosha, a ribonuclease III enzyme; and DGCR8, a double-stranded RNA binding protein. [4] [5] [6] (DGCR8 is the name used in mammalian genetics, abbreviated from "DiGeorge syndrome critical region 8"; the homologous protein in model organisms such as flies and worms is called Pasha, for Partner of Drosha.)
[1] [2] These short hairpin introns formed via atypical miRNA biogenesis pathways. [ 3 ] [ 4 ] Mirtrons arise from the spliced-out introns and are known to function in gene expression. Mirtrons were first identified in Drosophila melanogaster and Caenorhabditis elegans .
AGO2 (grey) in complex with a microRNA (light blue) and its target mRNA (dark blue) In humans, there are eight AGO family members, some of which are investigated intensively. However, even though AGO1–4 are capable of loading miRNA, endonuclease activity and thus RNAi-dependent gene silencing exclusively belongs to AGO2.
The RNA-induced silencing complex, or RISC, is a multiprotein complex, specifically a ribonucleoprotein, which functions in gene silencing via a variety of pathways at the transcriptional and translational levels. [1]
In the past it had always been said that the same miRNA precursor generates the same miRNA sequences. However, the advent of deep sequencing has now allowed researchers to detect a huge variability in miRNA biogenesis, meaning that from the same miRNA precursor many different sequences can be generated potentially have different targets, [ 3 ...
The miR-29 microRNA precursor, or pre-miRNA, is a small RNA molecule in the shape of a stem-loop or hairpin. Each arm of the hairpin can be processed into one member of a closely related family of short non-coding RNAs that are involved in regulating gene expression . [ 1 ]