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Caenorhabditis elegans is a free-living transparent nematode about 1 mm in length that lives in temperate soil environments. It is the type species of its genus. The name is a blend of the Greek caeno- (recent), rhabditis (rod-like) and Latin elegans (elegant). In 1900, Maupas initially named it Rhabditides elegans. Osche placed it in the subgenus Caenorhabditis in 1952, and in 1955, Dougherty raised Caenorhabditis to the status of genus.
A microRNA is a small single-stranded non-coding RNA molecule found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression. miRNAs function via base-pairing with complementary sequences within mRNA molecules. As a result, these mRNA molecules are silenced, by one or more of the following processes: (1) Cleavage of the mRNA strand into two pieces, (2) Destabilization of the mRNA through shortening of its poly(A) tail, and (3) Less efficient translation of the mRNA into proteins by ribosomes.
The Let-7 microRNA precursor was identified from a study of developmental timing in C. elegans, and was later shown to be part of a much larger class of non-coding RNAs termed microRNAs. miR-98 microRNA precursor from human is a let-7 family member. Let-7 miRNAs have now been predicted or experimentally confirmed in a wide range of species (MIPF0000002). miRNAs are initially transcribed in long transcripts called primary miRNAs (pri-miRNAs), which are processed in the nucleus by Drosha and Pasha to hairpin structures of about 70 nucleotide. These precursors (pre-miRNAs) are exported to the cytoplasm by exportin5, where they are subsequently processed by the enzyme Dicer to a ~22 nucleotide mature miRNA. The involvement of Dicer in miRNA processing demonstrates a relationship with the phenomenon of RNA interference.
In molecular biology lin-4 is a microRNA (miRNA) that was identified from a study of developmental timing in the nematode Caenorhabditis elegans. It was the first to be discovered of the miRNAs, a class of non-coding RNAs involved in gene regulation. miRNAs are transcribed as ~70 nucleotide precursors and subsequently processed by the Dicer enzyme to give a 21 nucleotide product. The extents of the hairpin precursors are not generally known and are estimated based on hairpin prediction. The products are thought to have regulatory roles through complete or partial complementarity to mRNA. The lin-4 gene has been found to lie within a 4.11kb intron of a separate host gene.
In molecular biology, mir-46 and mir-47 are microRNA expressed in C. elegans from related hairpin precursor sequences. The predicted hairpin precursor sequences for Drosophila mir-281 are also related and, hence, belong to this family. The hairpin precursors are predicted based on base pairing and cross-species conservation; their extents are not known. In this case, the mature sequences are expressed from the 3' arms of the hairpin precursors.
The miR-9 microRNA, is a short non-coding RNA gene involved in gene regulation. The mature ~21nt miRNAs are processed from hairpin precursor sequences by the Dicer enzyme. The dominant mature miRNA sequence is processed from the 5' arm of the mir-9 precursor, and from the 3' arm of the mir-79 precursor. The mature products are thought to have regulatory roles through complementarity to mRNA. In vertebrates, miR-9 is highly expressed in the brain, and is suggested to regulate neuronal differentiation. A number of specific targets of miR-9 have been proposed, including the transcription factor REST and its partner CoREST.
The miR-10 microRNA precursor is a short non-coding RNA gene involved in gene regulation. It is part of an RNA gene family which contains miR-10, miR-51, miR-57, miR-99 and miR-100. miR-10, miR-99 and miR-100 have now been predicted or experimentally confirmed in a wide range of species. mir-51 and mir-57 have currently only been identified in the nematode Caenorhabditis elegans.
The miR-124 microRNA precursor is a small non-coding RNA molecule that has been identified in flies, nematode worms, mouse and human. The mature ~21 nucleotide microRNAs are processed from hairpin precursor sequences by the Dicer enzyme, and in this case originates from the 3' arm. miR-124 has been found to be the most abundant microRNA expressed in neuronal cells. Experiments to alter expression of miR-124 in neural cells did not appear to affect differentiation. However these results are controversial since other reports have described a role for miR-124 during neuronal differentiation.
In molecular biology, mir-160 is a microRNA that has been predicted or experimentally confirmed in a range of plant species including Arabidopsis thaliana and Oryza sativa (rice). miR-160 is predicted to bind complementary sites in the untranslated regions of auxin response factor genes to regulate their expression. The hairpin precursors are predicted based on base pairing and cross-species conservation; their extents are not known. In this case, the mature sequence is excised from the 5' arm of the hairpin.
The miR-16 microRNA precursor family is a group of related small non-coding RNA genes that regulates gene expression. miR-16, miR-15, mir-195 and miR-497 are related microRNA precursor sequences from the mir-15 gene family. This microRNA family appears to be vertebrate specific and its members have been predicted or experimentally validated in a wide range of vertebrate species.
The mir-2 microRNA family includes the microRNA genes mir-2 and mir-13. Mir-2 is widespread in invertebrates, and it is the largest family of microRNAs in the model species Drosophila melanogaster. MicroRNAs from this family are produced from the 3' arm of the precursor hairpin. Leaman et al. showed that the miR-2 family regulates cell survival by translational repression of proapoptotic factors. Based on computational prediction of targets, a role in neural development and maintenance has been suggested.
The miR-92 microRNAs are short single stranded non-protein coding RNA fragments initially discovered incorporated into an RNP complex with a proposed role of processing RNA molecules and further RNP assembly. Mir-92 has been mapped to the human genome as part of a larger cluster at chromosome 13q31.3, where it is 22 nucleotides in length but exists in the genome as part of a longer precursor sequence. There is an exact replica of the mir-92 precursor on the X chromosome. MicroRNAs are endogenous triggers of the RNAi pathway which involves several ribonucleic proteins (RNPs) dedicated to repressing mRNA molecules via translation inhibition and/or induction of mRNA cleavage. miRNAs are themselves matured from their long RNA precursors by ribonucleic proteins as part of a 2 step biogenesis mechanism involving RNA polymerase 2.
Lin-28 homolog A is a protein that in humans is encoded by the LIN28 gene.
Victor R. Ambros is an American developmental biologist who discovered the first known microRNA (miRNA). He is a professor at the University of Massachusetts Medical School in Worcester, Massachusetts.
Gary Bruce Ruvkun is an American molecular biologist at Massachusetts General Hospital and professor of genetics at Harvard Medical School in Boston. Ruvkun discovered the mechanism by which lin-4, the first microRNA (miRNA) discovered by Victor Ambros, regulates the translation of target messenger RNAs via imperfect base-pairing to those targets, and discovered the second miRNA, let-7, and that it is conserved across animal phylogeny, including in humans. These miRNA discoveries revealed a new world of RNA regulation at an unprecedented small size scale, and the mechanism of that regulation. Ruvkun also discovered many features of insulin-like signaling in the regulation of aging and metabolism. He was elected a Member of the American Philosophical Society in 2019.
In molecular biology mir-84 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-241 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology, mir-786 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
David P. Bartel is an American molecular biologist best known for his work on microRNAs. Bartel is a Professor of Biology at the Massachusetts Institute of Technology, Member of the Whitehead Institute, and investigator of the Howard Hughes Medical Institute (HHMI).
In bioinformatics, TargetScan is a web server that predicts biological targets of microRNAs (miRNAs) by searching for the presence of sites that match the seed region of each miRNA. For many species, other types of sites, known as 3'-compensatory sites are also identified. These miRNA target predictions are regularly updated and improved by the laboratory of David Bartel in conjunction with the Whitehead Institute Bioinformatics and Research Computing Group.
References
- ↑ Li, M.; Jones-Rhoades, M. W.; Lau, N. C.; Bartel, D. P.; Rougvie, A. E. (2005). "Regulatory Mutations of mir-48, a C. Elegans let-7 Family MicroRNA, Cause Developmental Timing Defects". Developmental Cell. 9 (3): 415–422. doi: 10.1016/j.devcel.2005.08.002 . PMID 16139229.
- ↑ Lau, N. C.; Lim, L. P.; Weinstein, E. G.; Bartel, D. P. (2001). "An Abundant Class of Tiny RNAs with Probable Regulatory Roles in Caenorhabditis elegans". Science. 294 (5543): 858–862. Bibcode:2001Sci...294..858L. doi:10.1126/science.1065062. PMID 11679671. S2CID 43262684.
- 1 2 Abbott, A. L.; Alvarez-Saavedra, E.; Miska, E. A.; Lau, N. C.; Bartel, D. P.; Horvitz, H. R.; Ambros, V. (2005). "The let-7 MicroRNA Family Members mir-48, mir-84, and mir-241 Function Together to Regulate Developmental Timing in Caenorhabditis elegans". Developmental Cell. 9 (3): 403–414. doi: 10.1016/j.devcel.2005.07.009 . PMC 3969732 . PMID 16139228.
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