05-05-2014, 08:19 PM
Other RNA types
MiRNA – micro RNA
These are small non-coding RNA molecules (usually about 22 nucleotides long), and their main function is transcriptional and post-transcriptional regulation of gene expression. They were discovered during the 1990s, but their function was well defined one decade later, when they were grouped separately from other RNA molecules.
They are not found in prokaryotes – only in eukaryotes and some viruses whose genetic material consists out of DNA (viruses can also have only RNA). There is difference between animal and plant miRNAs, though. Animal miRNAs are complementary with target mRNA in only 6-8 nucleotides at the 5’ end; this region is called the seed region. Plant miRNAs, on the other hand, bind completely or almost completely to the target mRNAs, and they are not region-specific; they can bind to both 5’ and 3’ UTRs (untranslated regions) as well as to the coding region.
Once they are transcribed, they basically prevent the expression of a certain gene by binding to the specific mRNA that is awaiting translation. This complex of mRNA-miRNA is then degraded by cell’s mechanisms. Some 1000 miRNAs in humans are complementary to around 60% of our genes, so more than half of our genes can be regulated with this mechanism.
Even though the mechanism is well conserved among the species, micro RNAs themselves are not 100% specific. One micro RNA can bind to and silence more messenger RNAs. For example, studies have shown that on average, one miRNA targets around 7 mRNAs, but the number can go as high as 200 mRNAs, which means that one miRNA could affect the expression of hundreds of proteins. Also, one mRNA can be regulated by more micro RNAs.
The mechanism of silencing by micro RNA molecules is very interesting and it provides a lot of ground for manipulation, making research about it absolutely necessary, especially since a lot of diseases are connected to miRNAs, like heart and nervous diseases, obesity, etc.
MiRNA – micro RNA
These are small non-coding RNA molecules (usually about 22 nucleotides long), and their main function is transcriptional and post-transcriptional regulation of gene expression. They were discovered during the 1990s, but their function was well defined one decade later, when they were grouped separately from other RNA molecules.
They are not found in prokaryotes – only in eukaryotes and some viruses whose genetic material consists out of DNA (viruses can also have only RNA). There is difference between animal and plant miRNAs, though. Animal miRNAs are complementary with target mRNA in only 6-8 nucleotides at the 5’ end; this region is called the seed region. Plant miRNAs, on the other hand, bind completely or almost completely to the target mRNAs, and they are not region-specific; they can bind to both 5’ and 3’ UTRs (untranslated regions) as well as to the coding region.
Once they are transcribed, they basically prevent the expression of a certain gene by binding to the specific mRNA that is awaiting translation. This complex of mRNA-miRNA is then degraded by cell’s mechanisms. Some 1000 miRNAs in humans are complementary to around 60% of our genes, so more than half of our genes can be regulated with this mechanism.
Even though the mechanism is well conserved among the species, micro RNAs themselves are not 100% specific. One micro RNA can bind to and silence more messenger RNAs. For example, studies have shown that on average, one miRNA targets around 7 mRNAs, but the number can go as high as 200 mRNAs, which means that one miRNA could affect the expression of hundreds of proteins. Also, one mRNA can be regulated by more micro RNAs.
The mechanism of silencing by micro RNA molecules is very interesting and it provides a lot of ground for manipulation, making research about it absolutely necessary, especially since a lot of diseases are connected to miRNAs, like heart and nervous diseases, obesity, etc.
![[+]](https://www.biotechnologyforums.com/images/netpen-pro/collapse_collapsed.png)