Minsu Kim/minsu1

what is MicroRNA?

A microRNA (miRNA) is a small non-coding RNA molecule (containing about 22 nucleotides) found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression. miRNA are encoded in the genome as segments of longer transripts. their characteristic structure helps identify them and predict the target genes they might regulate. 

 

Synthesis and Function of miRNA

Structure of pre-miRNAs

overview of the structure of pri-miRNA showing cleavage

miRNAs are derived from precursor RNAs that are encoded by genes. their characteristic structure helps identify them and predict the target genes they might regulate. the functional form of a miRNA IS typically ~21 or 22 nucleotides. These short RNAs are generated by two RNA cleavage reactions from a longer RNA transcript (called a pri-RNA,  for "primary") that carries a hairpin-shaped scondary structure. The first cleavage liverates the stem- loop, called the pre-miRNA ; the second generates the mature miRNA from the pre-miRNA. The two cleavage reactions required to generate the miRNA grom these primary trnascipts are mediated by tow distinct RNases. One is Dicer, and the others is Drosha

miRNAs function via base-pairing with complementary sequences within mRNA. As a result, these mRNA molecules are silenced, by one or more of the following processes:

 

• To trigger destruction of the mRNA
• To interfere with translation of the mRNA
• Less efficient translation of the mRNA into proteins by ribosomes

 

miRNAs resemble the small interfering RNAs (siRNAs) of the RNA interference (RNAi) pathway, except miRNAs derive from regions of RNA transcripts that fold back on themselves to form short hairpins, whereas siRNAs derive from longer regions of double-stranded RNA. The human genome may encode over 1000 miRNAs, which are abundant in many mammalian cell types and appear to target about 60% of the genes of humans and other mammals

 

 

ESSAY

Can miRNA be available for a therapy about an intractable disease associated with a gene?

Gene is the most central element to produce proteins in the body, and everything in human is determined by gene. and disease like a cancer is associated with the gene. If so i thought 'Can miRNA be available for a therapy about an intractable disease associated with a gene?'. Because miRNA can be specified target gene and interfere the translation of proteins by ribosome.

So answer is 'YES. miRNA can be available for a therapy'. Already many scientists are studying about these problem and the relationship between cancer and miRNA has been found.

but limitation and difficulties also exist. 

first, Low permeation of miRNA by physical and physiological barriers of cancer tissue. Because abnormal vascular structure of tumor.

second, Unintended effects of miRNA. Because miRNAs target different pathways, unwanted gene suppression of cancer-suppressing genes may occur. This unintended effect may cause potential toxicity or reduce the effectiveness of the treatment.

related paper

MicroRNA and cancer
Martin D. Jansson, Anders H. Lund*
Biotech Research and Innovation Centre and Centre for Epigenetics, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen,
Denmark

 

Reference

https://en.wikipedia.org/wiki/MicroRNA#Target_prediction		http://www.ibric.org/myboard/read.php?Board=report&id=2489
molecular biology of the gene seventh edition-pearson		http://www.kosen21.org/info/kosenReport/reportView.do?articleSeq=759471