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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.
Oligonucleotides are short DNA or RNA molecules, oligomers, that have a wide range of applications in genetic testing, research, and forensics. Commonly made in the laboratory by solid-phase chemical synthesis, these small fragments of nucleic acids can be manufactured as single-stranded molecules with any user-specified sequence, and so are vital for artificial gene synthesis, polymerase chain reaction (PCR), DNA sequencing, molecular cloning and as molecular probes. In nature, oligonucleotides are usually found as small RNA molecules that function in the regulation of gene expression, or are degradation intermediates derived from the breakdown of larger nucleic acid molecules.
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA at first non-coding RNA molecules, typically 20–24 base pairs in length, similar to miRNA, and operating within the RNA interference (RNAi) pathway. It interferes with the expression of specific genes with complementary nucleotide sequences by degrading mRNA after transcription, preventing translation.
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-1 microRNA precursor is a small micro RNA that regulates its target protein's expression in the cell. microRNAs are transcribed as ~70 nucleotide precursors and subsequently processed by the Dicer enzyme to give products at ~22 nucleotides. In this case the mature sequence comes from the 3' arm of the precursor. The mature products are thought to have regulatory roles through complementarity to mRNA. In humans there are two distinct microRNAs that share an identical mature sequence, and these are called miR-1-1 and miR-1-2.
The mir-BART1 microRNA precursor is found in Human herpesvirus 4 and Cercopithicine herpesvirus 15. mir-BART1 is found in all stages of infection but expression is significantly elevated in the lytic stage. In Epstein-Barr virus, mir-BART1 is found in the intronic regions of the BART gene whose function is unknown. The mature sequence is excised from the 5' arm of the hairpin.
The mir-BART2 microRNA precursor found in Human herpesvirus 4 and Cercopithicine herpesvirus 15. mir-BART2 is expressed in all stages of infection but expression is significantly elevated in the lytic stage. In Epstein-Barr virus, mir-BART2 is found in the intronic regions of the BART gene whose function is unknown. mir-BART2 is thought to target the virally encoded DNA polymerase BALF5 for degradation. The mature sequence is excised from the 5' arm of the hairpin.
The mir-BHRF1-3 microRNA precursor found in Human herpesvirus 4. In Epstein-Barr virus, mir-BHRF1-3 is found in the 3' UTR of the BHRF1 gene, which is known to encode a distant Bcl-2 homolog. The mature sequence is excised from the 5' arm of the hairpin. Two other miRNA precursors were found in this reading frame, namely Mir-BHRF1-1 and Mir-BHRF1-2.
miR-96 microRNA precursor is a small non-coding RNA that regulates gene expression. microRNAs are transcribed as ~80 nucleotide precursors and subsequently processed by the Dicer enzyme to give a ~23 nucleotide products. In this case the mature sequence comes from the 5′ arm of the precursor. The mature products are thought to have regulatory roles through complementarity to mRNA.
Therapeutic Target Database (TTD) is a pharmaceutical and medical repository constructed by the Innovative Drug Research and Bioinformatics Group (IDRB) at Zhejiang University, China and the Bioinformatics and Drug Design Group at the National University of Singapore. It provides information about known and explored therapeutic protein and nucleic acid targets, the targeted disease, pathway information and the corresponding drugs directed at each of these targets. Detailed knowledge about target function, sequence, 3D structure, ligand binding properties, enzyme nomenclature and drug structure, therapeutic class, and clinical development status. TTD is freely accessible without any login requirement at https://idrblab.org/ttd/.
RNA interference (RNAi) is a biological process in which RNA molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression. Historically, RNAi was known by other names, including co-suppression, post-transcriptional gene silencing (PTGS), and quelling. The detailed study of each of these seemingly different processes elucidated that the identity of these phenomena were all actually RNAi. Andrew Fire and Craig C. Mello shared the 2006 Nobel Prize in Physiology or Medicine for their work on RNAi in the nematode worm Caenorhabditis elegans, which they published in 1998. Since the discovery of RNAi and its regulatory potentials, it has become evident that RNAi has immense potential in suppression of desired genes. RNAi is now known as precise, efficient, stable and better than antisense therapy for gene suppression. Antisense RNA produced intracellularly by an expression vector may be developed and find utility as novel therapeutic agents.
MiR-155 is a microRNA that in humans is encoded by the MIR155 host gene or MIR155HG. MiR-155 plays a role in various physiological and pathological processes. Exogenous molecular control in vivo of miR-155 expression may inhibit malignant growth, viral infections, and enhance the progression of cardiovascular diseases.
This microRNA database and microRNA targets databases is a compilation of databases and web portals and servers used for microRNAs and their targets. MicroRNAs (miRNAs) represent an important class of small non-coding RNAs (ncRNAs) that regulate gene expression by targeting messenger RNAs.
miR-146 is a family of microRNA precursors found in mammals, including humans. The ~22 nucleotide mature miRNA sequence is excised from the precursor hairpin by the enzyme Dicer. This sequence then associates with RISC which effects RNA interference.
VIRsiRNAdb is a database of siRNA/shRNA targeting viral genome regions.
In molecular biology mir-455 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-23 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology mir-3180 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms. The mir-10 microRNA precursor is a short non-coding RNA gene that is part of an RNA gene family which contains mir-3180-1, mir-3180-2, mir-3180-3, mir-3180-4 and mir-3180-5. They have now been predicted or experimentally confirmed in a wide range of cancers in humans. mir-3180 has currently only been identified in human Homo sapiens.
In molecular biology, Circular RNAs (circRNAs) refer to a class of circular RNA molecules found across all kingdoms of life. Studies in 2013 have suggested that circRNAs play important regulatory roles in miRNA activity. Researchers found that CDR1as circRNA acts as a miR-7 super-sponge that contains about 70 target sites from the same miR-7 at the same transcript. The other testis-specific circRNA, sex-determining region Y (Sry), also was found as a miR-138 sponge. About-mentioned examples suggesting that miRNA sponge effects achieved by circRNA formation may be a general phenomenon. As miR-7 modulates the expression of several oncogenes, ciRS-7/miR-7 interactions may play an important roles in cancer-related pathways. circRNA has also been shown in viral infection where it sequesters anti-viral protein to enhance viral replication.
MicroRNA-125 (miR-125) is a highly conserved microRNA family consisting of miR-125a and miR-125b. MiR-125 can be found throughout diverse species from nematode to humans. MiR-125 family members are involved in cell differentiation, proliferation and apoptosis as a result of targeting messenger RNAs related to these cellular processes. By affecting these cellular processes, miR-125 can cause promotion or suppression of pathological processes including carcinogenesis, muscle abnormalities, neurological disorders and pathologies of the immune system. Moreover, miR-125 also plays an important role in normal immune functions and was described to affect development and function of immune cells as well as playing role in immunological host defense in response to bacterial and viral infections.
References
- ↑ Qureshi A, Thakur N, Monga I, Thakur A, Kumar M (1 January 2014). "VIRmiRNA: a comprehensive resource for experimentally validated viral miRNAs and their targets". Database. 2014: bau103. doi:10.1093/database/bau103. PMC 4224276 . PMID 25380780.
