What Are Micro Rna Essay

1213 words - 5 pages

1. Introduction
1.1. What are micro RNAs?

Micro RNAs (miRNA) are small non-coding RNAs that are involved in regulating the translation of messenger RNA (mRNA). Over 1000 miRNAs have been identified which control approximately 60% of the protein coding genes1. The miRNAs are on average 23 nucleotides long, with nucleotides 2-7 acting as the seed region. The seed region is needed for specific mRNA interactions and mutations occur in this region it can disrupt the miRNA, mRNA Watson-Crick base pairing2.
mRNA is stabilized in the cytoplasm by adding a 5’ cap and a 3’ poly adenine tail, which prevents degradation by ribonucleases. The binding of miRNA can cause 3 events to occur; deadenylation, decapping, and 5’ to 3’ degradation1. Often in the 3’ untranslated region (UTR) there are AU rich elements (AREs) when the miRNA along with Argonaute 1, Argonaute 2 and Dicer1 is bound it allows rapid decay of the mRNA
1.2. miRNA biogenesis

miRNAs can be transcribed from their own genes; often there are clusters of these miRNA genes for example, C19MC, which is the largest human cluster3. Another place where miRNAs are coded for is within introns of other genes. The miRNAs are transcribed using either RNA polymerase II or III4,5, this is dependent on the specific promoter or terminator sequences for each gene. The new transcript is called the primary miRNA (pri-miRNA) and must undergo processing before it is able to regulate mRNA.
While in the nucleus the pri-miRNA undergoes the first cleavage, which is catalysed by Drosha, figure 1. Drosha is part of the RNase III family of enzymes and cleaves the transcript 11 base pairs from the double stranded/single stranded RNA junction3. For the cleavage to be accurate a molecular ruler in the form of Pasha (partner of Drosha) is used, this gives a pre-miRNA of approximately 70 nucleotides long6.
The exception to this rule is miRNA encoded in introns (mitrons), these are not cleaved but are instead processed using splicing from the immature mRNA transcript7.
After processing by Drosha, the pre-miRNA is then exported from the nucleus via Exportin5 (Exp5) which has Ran-GTP bound as co-factor. The binding of pre-miRNA is not a sequence specific event, the size of the double stranded stem and 3’ overhangs is the deciding factor to whether to transport the pre-miRNA into the cytoplasm3. This interaction with Exp5 protects the pre-miRNA from degradation, as when knocked out pre-miRNA levels do not accumulate in the nucleus3,8.
Once in the cytoplasm the pre-miRNA can then undergo the final cleavage step before becoming a mature miRNA. The RNase III Dicer cleaves the terminal loop of the pre-miRNA to leave a duplex, which is approximately 22 nucleotides in length3. Dicer is able to cleave without assistance, however the binding of TRBP (transactivating response RNA-binding protein) is thought to increase stability and improve the reactions efficiency9. In humans there is only one copy of a Dicer like protein,...

Find Another Essay On What Are Micro RNA

Translation and Protein Synthesis- the role of various RNA and the process of synthesis

709 words - 3 pages acids to those in amino acids. In essence, the hereditary instructions for building proteins are encoded in the nucleotide sequence of DNA and messenger-RNA. These, in turn, create the genetic code and the extreme relation between a cell's beginning nucleic acid transforming in to a developed protein.This entire process of protein synthesis begins with the attachment of messenger RNA to the small subunit of a ribosome that consists of a ribosomal

Characterizing the mRNA-binding activity of MEX-5

1747 words - 7 pages Specific Aim 2: What is the structure of the TZF domain of MEX-5 and what is its contribution to the RNA-binding specificity? The known structures of the CCCH-type TZF proteins highlight the fact that despite the presence of highly conserved residues in the primary sequence, these domains assume diverse conformations. In TIS11d the linker region is in an extended conformation, and the two ZFs are oriented in a parallel way. In MBNL-1, instead


886 words - 4 pages mutated strand. (10 - I, 15 A)Normal:DNA: ATG TGG AAC CGC TGC TGAmRNA: AUG UGG AAC CGC UGC UGAAmino acid: MET TRP ASN ARG CYS STOMutated:DNA: ATG TGG AAT CGC TGC TGAmRNA: AUG UGG AAU CGC UGC UGAAmino Acid: MET TRP ASN ARG CYS STOTranscription is the creating of a matching RNA copy of a sequence of DNA. RNA and DNA are both nucleic acids and use base pairs of nucleotides that can be converted back and forth from DNA to RNA by enzymes. A DNA sequence is

The Importance of Deoxy-ribo Nucleic Acid

986 words - 4 pages , thymine, cytosine, and guanine. All 4 of these are nucleic acids. These bond together with a Hydrogen bond. Adenine bonds with thymine, and cytosine bonds with guanine. The “backbone” of the DNA is the phosphate group and the ribo group bonded by covalent bonds. What is the difference between RNA and DNA? Well, as discussed before, there is one oxygen atom missing from the sugar in DNA, but there are more differences. DNA is a right handed

Detailed description of DNA replication and RNA transcription

1470 words - 6 pages chain.Primase joins RNA nucleotides into a primer, which initiates DNA replication. DNA ligase joins the final nucleotide, joining the sugar-phosphate backbones of all the Okazaki fragments into a continuous DNA strand on the lagging, and on the leading joins the 3’ end of the DNA that replaces the primer to the rest of the leading strand.After DNA replication, it provides the genetic code for what proteins to produce, depending on what the

DNA vs. RNA: Oncogenic Viruses

845 words - 4 pages , but it has to be highly protected, it doesn’t leave the nucleus where it is mostly found (Hall, 6). DNA’s function is to be a long-term storage and transmission of the genetic information (DNA vs RNA, 2014). Copies of certain instructions needed for proteins can be made in the form of RNA. It’s not an exact copy of what is found in DNA, but RNA can travel out of the nucleus with the instructions. RNA makes the proteins. These proteins carry

How Does DNA Control Cell Activity?

917 words - 4 pages . From RNA we also learned about transcription, protein structure, protein synthesis, enzyme production, and translation. We learned this through activities such as, our DNA study sheet, our cloning paper plasmid lab, out mutation activity, and our protein synthesis worksheet. In, DNA study sheet we were given background information for every few questions to answer about what DNA is, it’s structure, how the rings are built and where they match

RNA Evolution, RNA Function in RNA viruses and the Origin of Life

9784 words - 39 pages longer it attracted more matching nucleotides faster, causing chains to now form faster than they were breaking down.These chains are proposed as the first, primitive forms of life. In an RNA world, different forms of RNA compete with each other for free nucleotides and are subject to natural selection. The most efficient molecules of RNA, the ones able to efficiently catalyze their own reproduction, survived and evolved, forming modern

The Differences Between Prokaryotic and Eukaryotic Organisms

2171 words - 9 pages post-transcriptional gene silencing (PTGS), is another example of how prokaryotic and eukaryotic organisms process mRNA. One method of PTGS is RNA interference by the action of what are called small-interfering RNAs (siRNA) or micro RNAs (miRNA). These are short molecules of RNA that are complementary to specific sections of mRNA. During RNA interference these molecules bind to such regions and cause the breakdown of certain mRNAs via argonaute

DNA What is it?

1407 words - 6 pages coded. The origin of the code is directly related to the way the four nitrogenous bases are arranged in the DNA. It is important that DNA and RNA control protein synthesis. Proteins control both the cell's movement and it's structure. Proteins also direct production of lipids, carbohydrates, and nucleotides. DNA and RNA do not actually produce these proteins, but tell the cell what to make. (Heath, 111-113)For a cell to build a protein according


1166 words - 5 pages synthesized (b)double -stranded RNA must be synthesized (c)complementary strand of DNA must be synthesized from an RNA template (d)a complementary strand of DNA must be synthesized from a DNA template (e)none of the aboveThe definition of lysogeny is: (a)phage DNA is incorporated into host cell DNA (b)lysis of the host cell due to a phage (c)the period during replication when virions are not present (d) when the burst time takes an unusually long

Similar Essays

Micro Rna And Cardiovascular Analysis

1143 words - 5 pages Micro RNA and Cardiovascular Cardiovascular disease is the leading cause of deaths worldwide and is one of the main causes of morbidity and mortality in developed countries. The pathological process of the heart is related to altered expression of genes that are important for cardiac function. Thus micro RNAs have become known as key regulators of gene expression and the recent studies have suggested the potential importance of micro RNAs as

Micro Ribonucleic Acid Analysis

709 words - 3 pages Studies are being carried out using animal models such as mice and zebra fish to understand the importance of micro RNA in vascular development. Knockdown of micro RNA 126 in zebra fish resulted in loss of vascular integrity and haemorrhage during embryonic development (65). Overexpression of micro RNA 92a (66) induced severe defects in inter segmental vessel formation in zebra fish. An independent study reported that deletion of micro RNA 126

The Rna World Essay

1129 words - 5 pages Ribonucleic acid is a large part of the modern world as RNA (Ribonucleic acid) is one of the major macromolecules which are known for playing an essential role in all known forms of life. The most common function of RNA is that it is a copy of DNA and is used to create proteins and other organic compounds. To produce a certain protein, it activates the area of DNA that codes for a specific protein needed. Thus it replicates that section of DNA

Gene Expression Essay

699 words - 3 pages The process of gene expression is used by all known life known as eukaryotes which include multicellular organisms, prokaryotes like bacteria and Achaea, and viruses which generates the macromolecular machinery for life. Gene expression is what “turns on” the genes and makes a product. The products made could be an enzyme, a protein, or a control molecule. These products are often proteins, but in non-protein coding genes such as mRNA genes or