Why is RNA needed?
25758#22
At first, regulatory RNA was thought to be a eukaryotic phenomenon, a part of the explanation for why so much more transcription in higher organisms was seen than had been predicted. But as soon as researchers began to look for possible RNA regulators in bacteria, they turned up there as well. Currently, the ubiquitous nature of systems of RNA regulation of genes has been discussed as support for the RNA World theory. Bacterial small RNAs generally act via antisense pairing with mRNA to down-regulate its translation, either by affecting stability or affecting cis-binding ability. Riboswitches have also been discovered. They are cis-acting regulatory RNA sequences acting allosterically. They change shape when they bind metabolites so that they gain or lose the ability to bind chromatin to regulate expression of genes.
RNA
25758#0
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and DNA are nucleic acids, and, along with lipids, proteins and carbohydrates, constitute the four major macromolecules essential for all known forms of life. Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA it is more often found in nature as a single-strand folded onto itself, rather than a paired double-strand. Cellular organisms use messenger RNA (mRNA) to convey genetic information (using the nitrogenous bases of guanine, uracil, adenine, and cytosine, denoted by the letters G, U, A, and C) that directs synthesis of specific proteins. Many viruses encode their genetic information using an RNA genome.
RNA
25765#42
Another proposal is that the dual-molecule system we see today, where a nucleotide-based molecule is needed to synthesize protein, and a peptide-based (protein) molecule is needed to make nucleic acid polymers, represents the original form of life. This theory is called RNA-peptide coevolution, or the Peptide-RNA world, and offers a possible explanation for the rapid evolution of high-quality replication in RNA (since proteins are catalysts), with the disadvantage of having to postulate the coincident formation of two complex molecules, an enzyme (from peptides) and a RNA (from nucleotides). In this Peptide-RNA World scenario, RNA would have contained the instructions for life, while peptides (simple protein enzymes) would have accelerated key chemical reactions to carry out those instructions. The study leaves open the question of exactly how those primitive systems managed to replicate themselves — something neither the RNA World hypothesis nor the Peptide-RNA World theory can yet explain, unless polymerases (enzymes that rapidly assemble the RNA molecule) played a role.
RNA world
25758#5
The functional form of single-stranded RNA molecules, just like proteins, frequently requires a specific tertiary structure. The scaffold for this structure is provided by secondary structural elements that are hydrogen bonds within the molecule. This leads to several recognizable "domains" of secondary structure like hairpin loops, bulges, and internal loops. Since RNA is charged, metal ions such as Mg are needed to stabilise many secondary and tertiary structures.
RNA
201268#0
RNA polymerase (ribonucleic acid polymerase), both abbreviated RNAP or RNApol, official name DNA-directed RNA polymerase, is a member of a family of enzymes that are essential to life: they are found in all living organisms and many viruses. RNAP locally opens the double-stranded DNA (usually about four turns of the double helix) so that one strand of the exposed nucleotides can be used as a template for the synthesis of RNA, a process called transcription. A transcription factor and its associated transcription mediator complex must be attached to a DNA binding site called a promoter region before RNAP can initiate the DNA unwinding at that position. RNAP has intrinsic helicase activity, therefore no separate enzyme is needed to unwind the DNA (in contrast to DNA polymerase). RNAP not only initiates RNA transcription, it also guides the nucleotides into position, facilitates attachment and elongation, has intrinsic proofreading and replacement capabilities, and termination recognition capability. In eukaryotes, RNAP can build chains as long as 2.4 million nucleotides.
RNA polymerase
2065799#7
However, in 2012, the Australian Safe Food Foundation alleged that the RNA trigger designed to change wheat's starch content might interfere with the gene for a human liver enzyme. Supporters countered that RNA does not appear to make it past human saliva or stomach acids. The US National Honey Bee Advisory Board told EPA that using RNAi would put natural systems at "the epitome of risk". The beekeepers cautioned that pollinators could be hurt by unintended effects and that the genomes of many insects are still unknown. Other unassessed risks include ecological (given the need for sustained presence for herbicide and other applications) and the possible for RNA drift across species boundaries.
Biopesticide
34255387#2
The enzyme belongs to the group of oxidoreductases according to the EC classification and is dependent on FAD as cofactor, thus it was classified as an external flavoprotein monooxygenase (designated as type E). It forms a two-component system with a reductase (StyB, StyA2B). The reductase utilizes solely NADH to reduce the FAD, which is then transferred to the styrene monooxygenase (StyA, StyA1). Two types of that enzyme are described so far: StyA/StyB (designated E1), first described from "Pseudomonas" species, and StyA1/StyA2B (designated E2), first described from Actinobacteria. The E1-type is more abundant in nature and comprises a single monooxygenase (StyA) supported by a single reductase (StyB), whereas the E2-type has a major monooxygenase (StyA1) which is supported by fusion protein of a monooxygenase and reductase (StyA2B). The latter one is the source of reduced FAD for the monooxygenase subunits and has some side activity as a monooxygenase. So far all styrene monooxygenases perform enantioselective epoxidations of styrene and chemically analogous compounds, which makes them interesting for biotechnological applications.
Styrene monooxygenase
2153382#1
Ġ is used in some Arabic transliteration schemes, such as DIN 31635 and ISO 233, to represent the letter (ġain).
Ġ
18937539#9
On January 20, Lt. General Katawal, Royal Nepalese Army (RNA) Chief of General Staff, told Ambassador James F. Moriarty that he was worried that the government did not have a unified strategy for tackling the Maoist insurgency. Katawal reiterated that there was no purely military solution to the insurgency; the RNA could only work to create space for a negotiated political solution. He noted that the civilian government should lead the effort to inform its citizens about Nepal's overall plan to tackle the insurgency. Katawal stressed that a civilian government needed to explain to the people what the military was doing and why, especially why the government needed to restrict civil liberties.
Rookmangud Katawal
14596479#0
Ẑ is a Latin script letter, the letter Z with a circumflex, used for transliteration of the Cyrillic letter Ѕ in ISO 9 family of transliteration standards. The lower case version of the letter is ẑ.
Ẑ
55853074#1
s͎ is represented in Unicode by an s and U+034E (Combining Upwards Arrow Below).
S͎