The Discovery That Double Stranded Rna Can Efficiently Silence Gene Expression

Structurally, miRNAs are initially transcribed from the genome as a long primary transcript that are cleaved or undergoes sequential processing by the RNAse III endonucleases Drosha and Dicer to yield the 17-23 mature nucleotide species (Kim, 2005). Mature miRNAs enters the RNA-induced silencing complex (RISC), thus a multiprotein complex that separate the mature strand from passenger strand and assists the interaction of mRNAs with miRNA that contain complementary sequences (Bader, 2012). As a result, mRNAs targeted by miRNA loads are either degraded or silenced in order not to be translated into protein. In the genome, a given miRNA can regulate several hundred transcripts whose molecules function within various cellular pathways including cell proliferation and apoptosis. To date, more than 50% of the activities of all protein-coding genes in mammals are controlled by miRNAs and greatly contributes to cell-type specific profiles of protein expression

In the second paper, “Novel RNA Modifications in the Nervous System: Form and Function,” Lee discusses the role of several novel RNA modification in the physiological setting of the nervous system. RNA editing plays a major role in many pathologies; for example, loss of normal function in an m6a demethylase, FTO, has been connected with cancer, ADHD, and Alzheimer’s. Other RNA modifications are necessary for proper development of the central nervous system. NSUN2 is an m5C RNA modification heavily implicated in embryogenesis, especially in the brain. Mutation of the NSUN2 gene is correlated with intellectual disability, developmental delay, and facial dysmorphism. The aforementioned A-to-I RNA edit is also enriched in the brain, and is necessary for the proper function of genes such as GluA2, which without modification leads to postnatal death. GluA2 is also implicated in glutamate reception by neurons, and consequently in the mechanisms of addiction. Furthermore, A-to-I RNA editing failure been linked with several chronic diseases, including

DNA is double stranded, while RNA is single stranded. DNA is only found inside the nucleus and RNA can travel outside of the nucleus. There is one type of DNA and 3 kinds of RNA. DNA has a nitrogenous base named thymine that pairs with adenine. In RNA instead of Thymine it has Uracil that pairs with adenine.

The RNA-induced-silencing complex is used for gene regulation and in defense against viral and bacterial infections. The RISC is loaded with small dsRNAs that will guide the complex through base-pairing interactions to specific messenger RNA targets, which the RISC will help degrade. Once degraded, no more protein can be made from these mRNAs. The RNA-induced silencing complex can silence targeted genes through several mechanisms. It can work to repress translation during protein synthesis, interfere with the transcript level through mRNA degradation, or work at the level of the genome itself and eliminate DNA/form degrading materials. Heterochromatin is a degrading material that can be created to modify or suppress genes in the RISC (MacRae

RNA interference takes advantage of an intermediate step between DNA and protein. DNA acts as a blueprint for the final protein by using messenger RNA (mRNA) . The mRNA is a messenger molecule between DNA and protein synthesis. There is a two steps process need to be completed in order to go from gene to protein. The first step in protein synthesis is transcription, it takes place in a cell’s nucleus, where the DNA template is used to make a single strand of mRNA. Then, the messenger RNA exits the nucleus and enters the cytoplasm. Now it serves as the template for making the protein. After that, with the help of several different molecules, a string of amino acids forms due to the order of the mRNA bases. This process is called translation

Caenorhabditi elegans?has become an important organism in which to study processes that go awry in human diseases since over 50 yeas ago when Sydney Brenner had the foresight to develop the nematode (round worm)?Caenorhabditis elegans?as a genetic model for understanding questions of developmental biology and neurobiology. There are several attractive features that make Caenorhabditi elegans?an ideal organism for the study of gene regulation and function. First of all, C. elegans is a eukaryote, which means that it shares cellular and molecular structures and control pathways with higher organisms. At least 38% of the C. elegans protein-coding genes have predicted orthologous in the human genome,

There have been many studies conducted using RNAi but very few have been conducted with using the Danio rerio, the zebrafish. However, the zebrafish is ideal for this study due to the fact that 70% of human genes share at least one obvious zebrafish orthologue. (Kerstin Howe, et. al, 2014) Furthermore, the zebrafish is one of the few species that posses the GABRB3 gene, which is linked to Aspergers Syndrome. The GABRB3 gene regulates the functioning of a neurotransmitter called gamma-aminobutyric acid. It has been said that the RNAi can be used to knock down the function of the gene, therefore “silencing” it. (Gopalakrishna; Slack; 2002)

microRNAs (miRNAs) are a short ( about 22-26 nt length ) non coding RNA that involved in regulating gene expression at the level of post-transcription or translation and apparently control a broad range of processes of multicellular organisms including cellular differentiation, proliferation and apoptosis via targeting mRNA and cause their degradation or protein translation inhibition. miRNA transcribed from long pri-miRNA in the nucleus then processed by Dicer enzyme in the cytoplasm to form mature miRNA that incorporate in RNA induced silencing complex (RISC) to enhance their functions.

Since shRNA does not interact with the Drosha/DGCR8 microprocessor complex, this RNA must be designed with care in order to achieve correct downstream processing and gene suppression.1 Proper dosage of shRNAs is another factor to consider, as it has been found that they may saturate the endogenous pathway and disrupt natural miRNAs.4

RNA stands for ‘ribonucleic acid’ and it is present in all living cells. RNA’s main job is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins. RNA is similar in structure and properties to DNA. RNA, however, has only a single strand of bases. Also, rather than having the base thymine, RNA has the base uracil. Anyways, the guide RNA is composed of a miniscule pre-designed RNA sequence. This sequence is roughly 20 bases long and is located within a longer RNA framework. The scaffold part of the RNA binds to DNA and the pre-designed sequence. It ‘guides’ Cas9 to the right part of the genome. This makes sure that the Cas9 enzyme cuts at the right point in the genome.

RNAi is defined as a mechanism of gene-silencing produced by small RNA fragments (siRNA/miRNA/shRNA) and it also can be described as posttranscriptional gene silencing3. These small RNAs have the ability to selectively bind and cleave cellular mRNAs and prevent their further expression3. This function holds great significance in cancer treatment and cell self-repairing1,3. The mechanism of RNAi therapy consists of multiple steps. Briefly, a double-strand small RNA fragment (~20bp) firstly incorporates into a multiprotein complex, RNA-Induced Silencing Complex (RISC), and their double strands starts unwinding after being activated. The single-stranded small RNAs product then guided activated RISC to identify mRNAs that are complementary to this single-stranded small RNA3,4. Once identified, this mRNA is cleaved by endoribonucleases and then degraded by exoribonucleases in

First, piwi-interacting RNAs (piRNAs) are in the same class of small RNAs alone with miRNA, both RNAs requires a class of enzymes called Dicer to modify them so coevolution between piRNA and miRNA becomes possible. piRNAs are most abundantly expressed in Nematostella, Amphimedon and some mammalians. Class I piRNAs, also called mammalian pachytene piRNAs and class II piRNAs which used to silent some genes are both expressed in mammals and fruit flies prove that these piRNA classes may exist since the origin of metazoans. The piRNA evolution pattern states those two types of small riboregulators have been present since the very early stage of animal life evolution and

The first introduction of Caenorhabditis elegans (C.elegans) was in the early 1960s, by Sydney Brenner who used it as a model system to explore the genetics dissections of development, neurobiology and behaviour; he won the Nobel Prize in 2002 for his work on C.elegans. The C.elegans model specialises in having a short life span, retaining a low maintenance cost and its ability to grow the organism in a large population, and a small concern for animal rights issues. Each of these features is a key part to the power of C.elegans being used as a tool for understanding the functional genomics of diseases.

MicroRNAs are short non-coding RNAs play main role in human diseases; it deregulates the RNA and represses the translation process by controlling gene expression. Some deregulated miRNAs express deferentially such as mir-125b, mir-145, mir-155, and mir-21 leads for partition between cancer and normal tissues. miRNAs expression with particular cancer biopathologic features in breast, such as tumor stage, estrogen and progesterone receptor expression, vascular invasion, or proliferation index. Exiqon microarrays analysis revealed that the most of the miRNAs down regulated in hereditary breast cancer by comparing the normal and cancer tissues, and by using mechanism of tumor progression and also pathway enrichment analysis showed

One of the fundamental discoveries of the 20th century was that DNA was the genetic code’s physical structure (Watson & Crick, 1953) and, since then, many studies have disclosed the complicated pattern of regulation and expression of genes, which involve RNA synthesis and its subsequent translation into proteins.