Extended part for Chamomile - microRNA

microRNA (Wikipedia)
miRNAs can bind to target messenger RNA (mRNA) transcripts of protein-coding genes and negatively control their translation or cause mRNA degradation.
It is of key importance (for miRNAs) to identify the miRNA targets accurately.
Plant miRNAs usually have near-perfect pairing with their mRNA targets, which induces gene repression through cleavage of the target transcripts. In contrast, animal miRNAs are able to recognize their target mRNAs by using as few as 6–8 nucleotides (the seed region) at the 5' end of the miRNA, which is not enough pairing to induce cleavage of the target mRNAs. Combinatorial regulation is a feature of miRNA regulation in animals. A given miRNA may have hundreds of different mRNA targets, and a given target might be regulated by multiple miRNAs.

Under a standard nomenclature system, names are assigned to experimentally confirmed miRNAs before publication:
The prefix:-

• "miR" is followed by a dash and a number, the latter often indicating order of naming. For example, miR-124 was named and likely discovered prior to miR-456.
• Species of origin is designated with a three-letter prefix, e.g., hsa-miR-124 is a human (Homo sapiens) miRNA and oar-miR-124 is a sheep (Ovis aries) miRNA. Other common prefixes include "v" for viral (miRNA encoded by a viral genome) and "d" for Drosophila miRNA (a fruit fly commonly studied in genetic research).
• A capitalized "miR-" refers to the mature form of the miRNA, while the uncapitalized "mir-" refers to the pre-miRNA and the pri-miRNA. The miRNAs encoding genes are also named using the same three-letter prefix according to the conventions of the organism gene nomenclature.

The suffix:-

• Pre-miRNAs, pri-miRNAs and genes that lead to 100% identical mature miRNAs but that are located at different places in the genome are indicated with an additional dash-number suffix. For example, the pre-miRNAs hsa-mir-194-1 and hsa-mir-194-2 lead to an identical mature miRNA (hsa-miR-194) but are from genes located in different genome regions.

• miRNAs with nearly identical sequences except for one or two nucleotides are annotated with an additional lower case letter. For example, miR-124a is closely related to miR-124b. For example:
  hsa-miR-181a: aacauucaACgcugucggugAgu
  hsa-miR-181b: aacauucaUUgcugucggugGgu

The function of miRNAs appears to be in gene regulation. miRNA is complementary to a part of one or more mRNAs.

• In animals the match-ups are imperfect, miRNAs usually complementary to a site in the 3' UTR (three prime untranslated region) whereas plant miRNAs are usually complementary to coding regions of mRNAs.

• Perfect or near perfect base pairing with the target RNA promotes cleavage of the RNA. This is the primary mode of plant miRNAs.
  miRNAs appear to regulate the development and function of the nervous system. Neural miRNAs are involved at various stages of synaptic development, including dendritogenesis (involving miR-132, miR-134 and miR-124), synapse formation and synapse maturation (where miR-134 and miR-138 are thought to be involved).
  Some studies find altered miRNA expression in Alzheimer's disease, as well as schizophrenia, bipolar disorder, major depression and anxiety disorders.

Chronic alcohol abuse results in persistent changes in brain function mediated in part by alterations in gene expression. miRNA regulates many downstream genes and is significant in respect of the reorganization of synaptic connections or long term neural adaptations connected with the behavioral change caused by alcohol withdrawal and/or dependence. Up to 35 different miRNAs have been found to be altered in the alcoholic post-mortem brain.

Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA (dsRNA) at first non-coding RNA molecules, typically 20-24 (normally 21) 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.
siRNAs delivered via lipid based nanoparticles have been shown to have therapeutic potential for central nervous system (CNS) disorders. Central nervous disorders are not uncommon, but the blood brain barrier (BBB) often blocks access of potential therapeutics to the brain. siRNAs that target and silence efflux proteins on the BBB surface have been shown to create an increase in BBB permeability. siRNA delivered via lipid based nanoparticles is able to cross the BBB completely.

See also: Role of 5′- and 3′-untranslated regions of mRNAs in human diseases

Posted on October 26, 2022 06:20 AM by lunababy22