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MicroRNA (miRNA) are small, single-stranded, non-coding RNA molecules containing 21 to 23 nucleotides. Found in plants, animals and some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. miRNAs base-pair to complementary sequences in mRNA molecules, then gene silence said mRNA molecules by one or more of the following processes:
- Cleavage of mRNA strand into two pieces,
- Destabilization of mRNA by shortening its poly(A) tail, or
- Translation of mRNA into proteins.
Small RNA (sRNA) are polymeric RNA molecules that are less than 200 nucleotides in length, and are usually non-coding. RNA silencing is often a function of these molecules, with the most common and well-studied example being RNA interference (RNAi), in which endogenously expressed microRNA (miRNA) or exogenously derived small interfering RNA (siRNA) induces the degradation of complementary messenger RNA. Other classes of small RNA have been identified, including piwi-interacting RNA (piRNA) and its subspecies repeat associated small interfering RNA (rasiRNA). Small RNA "is unable to induce RNAi alone, and to accomplish the task it must form the core of the RNA–protein complex termed the RNA-induced silencing complex (RISC), specifically with Argonaute protein".
The mir-172 microRNA is thought to target mRNAs coding for APETALA2-like transcription factors. It has been verified experimentally in the model plant, Arabidopsis thaliana. The mature sequence is excised from the 3' arm of the hairpin.
In molecular biology miR-181 microRNA precursor is a small non-coding RNA molecule. MicroRNAs (miRNAs) are transcribed as ~70 nucleotide precursors and subsequently processed by the RNase-III type enzyme Dicer to give a ~22 nucleotide mature product. In this case the mature sequence comes from the 5' arm of the precursor. They target and modulate protein expression by inhibiting translation and / or inducing degradation of target messenger RNAs. This new class of genes has recently been shown to play a central role in malignant transformation. miRNA are downregulated in many tumors and thus appear to function as tumor suppressor genes. The mature products miR-181a, miR-181b, miR-181c or miR-181d are thought to have regulatory roles at posttranscriptional level, through complementarity to target mRNAs. miR-181 which has been predicted or experimentally confirmed in a wide number of vertebrate species as rat, zebrafish, and in the pufferfish.
mir-395 is a non-coding RNA called a microRNA that was identified in both Arabidopsis thaliana and Oryza sativa computationally and was later experimentally verified. mir-395 is thought to target mRNAs coding for ATP sulphurylases. The mature sequence is excised from the 3' arm of the hairpin.
In molecular biology mir-210 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-339 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms. miR-339-5p expression was associated with overall survival in breast cancer.
In molecular biology mir-186 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-873 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-390 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-394 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-396 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-397 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-403 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-408 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-444 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-474 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-824 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
DCL1 is a gene in plants that codes for the DCL1 protein, a ribonuclease III enzyme involved in processing double-stranded RNA (dsRNA) and microRNA (miRNA). Although DCL1, also called Endoribonuclease Dicer homolog 1, is named for its homology with the metazoan protein Dicer, its role in miRNA biogenesis is somewhat different, due to substantial differences in miRNA maturation processes between plants and animals, as well due to additional downstream plant-specific pathways, where DCL1 paralogs like DCL4 participate, such Trans-acting siRNA biogenesis.
Jian-Kang Zhu is a plant scientist, researcher and academic. He is a Senior Principal Investigator in the Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences (CAS). He is also the Academic Director of CAS Center of Excellence in Plant Sciences.
