miRNA Biogenesis: A Dynamic Pathway

The assembly of the miRNA biogenesis machinery starts during miRNA gene transcription. There is crosstalk between components of the miRNA biogenesis and mRNA splicing machineries, which mutually regulate each other. miRNA production is regulated tissue-specifically and varies depending on each pri-miRNA. The miRNA pathway is a fluid, dynamic, and interconnected process. MicroRNAs (miRNAs) modulate plant homeostasis through the inactivation of specific mRNAs, especially those encoding transcription factors. A delicate spatial/temporal balance between a miRNA and its targets is central to achieving the appropriate biological outcomes. In this review we discuss our growing understanding of the dynamic regulation of miRNA biogenesis. We put special emphasis on crosstalk between miRNA biogenesis and other cellular processes such as transcription and splicing. We also discuss how the pathway is regulated in specific tissues to achieve harmonious plant development through a subtle balance between gene expression and silencing. MicroRNAs (miRNAs) modulate plant homeostasis through the inactivation of specific mRNAs, especially those encoding transcription factors. A delicate spatial/temporal balance between a miRNA and its targets is central to achieving the appropriate biological outcomes. In this review we discuss our growing understanding of the dynamic regulation of miRNA biogenesis. We put special emphasis on crosstalk between miRNA biogenesis and other cellular processes such as transcription and splicing. We also discuss how the pathway is regulated in specific tissues to achieve harmonious plant development through a subtle balance between gene expression and silencing. the AGO proteins, loaded with small RNAs (sRNAs), catalyze the transcriptional or post-transcriptional silencing of target genes. There are 10 members of the AGO family of proteins in Arabidopsis. highly conserved tandem heptapeptide repeats (Y–S–P–T–S–P–S) located within the C-terminal end of the largest subunit of RNAPII. Post-translational modifications of the RNAPII-CTD regulate RNAPII activity, the recruitment of transcription factors, and RNA processing. homologs of the human DICER protein. DCLs are RNase III endonucleases that process long double-stranded RNA (dsRNA) into sRNA. subnuclear speckles that contain pri-miRNAs and several components of the miRNA biogenesis machinery. a methyltransferase that methylates the 3′ nucleotides of sRNA duplexes, protecting them from uridylation-triggered degradation. DCL1-dependent ∼21 nt sRNAs that guide the RISC complex to target genes, inducing their cleavage or translational inhibition. a protein complex formed by two subunits, CBP20 and CBP80, that binds to the mRNA 5′-cap. The CBC acts in many aspects of mRNA metabolism including mRNA splicing, export, and decapping protection. defined as the set of proteins required for the processing of a pri-miRNA into a mature miRNA duplex. protein complex responsible for triggering sRNA-mediated gene silencing. It contains an Argonaute protein, a loaded sRNA, and accessory proteins. group of small (20–25 nt) single-stranded RNAs derived from dsRNA precursors that induce transcriptional (TGS) and post-transcriptional (PTGS) gene silencing.