Skip to main content

Advertisement

Fig. 1 | Biotechnology for Biofuels

Fig. 1

From: Mechanisms of microRNA-mediated gene regulation in unicellular model alga Chlamydomonas reinhardtii

Fig. 1

A schematic of canonical miRNA biogenesis in animals, plants and C. reinhardtii. Mature miRNAs are indicated in red, and miRNA* strands are in black. Homologs with similar functions are shown in the same color. Gray areas in the C. reinhardtii panel indicate unknown factors or processes. a In animals, miRNA genes (MIR) are embedded within the introns of protein-coding genes (Gene A, for example) and transcribed by RNA polymerase II (Pol II). Canonical animal miRNAs are processed by the nuclear RNase III enzyme Drosha, in cooperation with Pasha and Ars2. The precursor miRNA (pre-miRNA) is exported from the nucleus to the cytoplasm by Export5, and it is subsequently cut into a miRNA/miRNA* duplex with 2 nt 3′ overhangs by Dicer, acting together with Loqs. One strand of the duplex is degraded, and the other mature miRNA is loaded onto RISC, whose core component is an AGO protein. b In plants, MIR genes are embedded within the noncoding sequences between protein-coding genes (Gene A and Gene B, for example) and are also transcribed by Pol II. Canonical plant miRNAs are produced by the nuclear RNase III Dicer-like1 (DCL1), assisted by HYL1/DRB1 and SERRATE (SE). DCL1 is responsible for both steps of miRNA processing to produce the miRNA/miRNA* duplex, which is then transported to the cytoplasm by HASTY. The miRNA/miRNA* duplex undergoes 2′-O-methylation modification by HEN1 at the 3′ end. One strand of the methylated duplex is degraded, and the other mature miRNA is loaded onto RISC, whose core component is an AGO protein. Plant miRNAs that are not methylated are subject to 3′ end uridylation by the poly(U) polymerase HESO1, resulting in subsequent degradation. c In Chlamydomonas, MIR genes are embedded within the introns of protein-coding genes (Gene A, for example) and transcribed by Pol II, similar to animal MIR. Chlamydomonas miRNAs are processed by the nuclear RNase III enzyme CrDCL3, in cooperation with DUS16. MUT68 is involved in 3′ end uridylation of miRNAs and may mediate miRNA degradation in cooperation with RRP6. The export protein responsible for transporting Chlamydomonas miRNAs from the nucleus to the cytoplasm is unknown. Whether mature miRNAs in C. reinhardtii are methylated is also presently unknown (gray areas in the diagram)

Back to article page