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U6 SnRNA
U6 snRNA is the non-coding small nuclear RNA (snRNA) component of U6 snRNP (''small nuclear ribonucleoprotein''), an RNA-protein complex that combines with other snRNPs, unmodified pre-mRNA, and various other proteins to assemble a spliceosome, a large RNA-protein molecular complex that catalyzes the excision of introns from pre-mRNA. Splicing, or the removal of introns, is a major aspect of post-transcriptional modification and takes place only in the nucleus of eukaryotes. The RNA sequence of U6 is the most highly conserved across species of all five of the snRNAs involved in the spliceosome, suggesting that the function of the U6 snRNA has remained both crucial and unchanged through evolution. It is common in vertebrate genomes to find many copies of the U6 snRNA gene or U6-derived pseudogenes. This prevalence of "back-ups" of the U6 snRNA gene in vertebrates further implies its evolutionary importance to organism viability. The U6 snRNA gene has been isolated in many organism ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Structure
Protein secondary structure is the three dimensional conformational isomerism, form of ''local segments'' of proteins. The two most common Protein structure#Secondary structure, secondary structural elements are alpha helix, alpha helices and beta sheets, though beta turns and omega loops occur as well. Secondary structure elements typically spontaneously form as an intermediate before the protein protein folding, folds into its three dimensional protein tertiary structure, tertiary structure. Secondary structure is formally defined by the pattern of hydrogen bonds between the Amine, amino hydrogen and carboxyl oxygen atoms in the peptide backbone chain, backbone. Secondary structure may alternatively be defined based on the regular pattern of backbone Dihedral angle#Dihedral angles of proteins, dihedral angles in a particular region of the Ramachandran plot regardless of whether it has the correct hydrogen bonds. The concept of secondary structure was first introduced by Kaj Ulrik ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudogenes
Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Most arise as superfluous copies of functional genes, either directly by DNA duplication or indirectly by reverse transcription of an mRNA transcript. Pseudogenes are usually identified when genome sequence analysis finds gene-like sequences that lack regulatory sequences needed for transcription or translation, or whose coding sequences are obviously defective due to frameshifts or premature stop codons. Most non-bacterial genomes contain many pseudogenes, often as many as functional genes. This is not surprising, since various biological processes are expected to accidentally create pseudogenes, and there are no specialized mechanisms to remove them from genomes. Eventually pseudogenes may be deleted from their genomes by chance DNA replication or DNA repair errors, or they may accumulate so many mutational changes that they are no longer recognizable as former genes. Analysis of these degeneration ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
U6atac Minor Spliceosomal RNA
U6atac minor spliceosomal RNA is a non-coding RNA which is an essential component of the minor U12-type spliceosome complex. The U12-type spliceosome is required for removal of the rarer class of eukaryotic introns (AT-AC, U12-type). U6atac snRNA is proposed to form a base-paired complex with another spliceosomal RNA U4atac via two stem loop regions. These interacting stem loops have been shown to be required for in vivo splicing. U6atac is the functional analog of U6 spliceosomal RNA U6 snRNA is the non-coding small nuclear RNA (snRNA) component of U6 snRNP (''small nuclear ribonucleoprotein''), an RNA-protein complex that combines with other snRNPs, unmodified pre-mRNA, and various other proteins to assemble a spliceosome, ... in the major U2-type spliceosomal complex. References * External links * Non-coding RNA Spliceosome RNA splicing {{molecular-cell-biology-stub fr:ARN splicéosomal U4atac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prp24
Prp24 (precursor RNA processing, gene 24) is a protein part of the pre-messenger RNA splicing process and aids the binding of U6 snRNA to U4 snRNA during the formation of spliceosomes. Found in eukaryotes from yeast to ''E. coli'', fungi, and humans, Prp24 was initially discovered to be an important element of RNA splicing in 1989. Mutations in Prp24 were later discovered in 1991 to suppress mutations in U4 that resulted in cold-sensitive strains of yeast, indicating its involvement in the reformation of the U4/U6 duplex after the catalytic steps of splicing. Biological Role The process of spliceosome formation involves the U4 and U6 snRNPs associating and forming a di-snRNP in the cell nucleus. This di-snRNP then recruits another member ( U5) to become a tri-snRNP. U6 must then dissociate from U4 to bond with U2 and become catalytically active. Once splicing has been done, U6 must dissociate from the spliceosome and bond back with U4 to restart the cycle. Prp24 has been shown ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lsm Ring
In molecular biology, LSm proteins are a family of RNA-binding proteins found in virtually every cellular organism. LSm is a contraction of 'like Sm', because the first identified members of the LSm protein family were the Sm proteins. LSm proteins are defined by a characteristic three-dimensional structure and their assembly into rings of six or seven individual LSm protein molecules, and play a large number of various roles in mRNA processing and regulation. The Sm proteins were first discovered as antigens targeted by so-called anti-Sm antibodies in a patient with a form of systemic lupus erythematosus (SLE), a debilitating autoimmune disease. They were named Sm proteins in honor of Stephanie Smith, a patient who suffered from SLE. Other proteins with very similar structures were subsequently discovered and named LSm proteins. New members of the LSm protein family continue to be identified and reported. Proteins with similar structures are grouped into a hierarchy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
U4 Spliceosomal RNA
The U4 small nuclear Ribo-Nucleic Acid (U4 snRNA) is a non-coding RNA component of the major or U2-dependent spliceosome – a eukaryotic molecular machine involved in the splicing of pre-messenger RNA (pre-mRNA). It forms a duplex with U6, and with each splicing round, it is displaced from the U6 snRNA (and the spliceosome) in an ATP-dependent manner, allowing U6 to re-fold and create the active site for splicing catalysis. A recycling process involving protein Brr2 releases U4 from U6, while protein Prp24 re-anneals U4 and U6. The crystal structure of a 5′ stem-loop of U4 in complex with a binding protein has been solved. Biological role The U4 snRNA has been shown to exist in a number of different formats including: bound to proteins as a small nuclear Ribo-Nuclear Protein snRNP, involved with the U6 snRNA in the di-snRNP, as well as involved with both the U6 snRNA and the U5 snRNA in the tri-snRNP. The different formats have been proposed to coincide with different temp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stem-loop
Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence when read in opposite directions, base-pair to form a double helix that ends in an unpaired loop. The resulting structure is a key building block of many RNA secondary structures. As an important secondary structure of RNA, it can direct RNA folding, protect structural stability for messenger RNA (mRNA), provide recognition sites for RNA binding proteins, and serve as a substrate for enzymatic reactions. Formation and stability The formation of a stem-loop structure is dependent on the stability of the resulting helix and loop regions. The first prerequisite is the presence of a sequence that can fold back on itself to form a paired double helix. The stability of this helix is determined by its length, the number of mismatches or bulges it co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Site
In biology and biochemistry, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of amino acid residues that form temporary bonds with the substrate (binding site) and residues that catalyse a reaction of that substrate (catalytic site). Although the active site occupies only ~10–20% of the volume of an enzyme, it is the most important part as it directly catalyzes the chemical reaction. It usually consists of three to four amino acids, while other amino acids within the protein are required to maintain the tertiary structure of the enzymes. Each active site is evolved to be optimised to bind a particular substrate and catalyse a particular reaction, resulting in high specificity. This specificity is determined by the arrangement of amino acids within the active site and the structure of the substrates. Sometimes enzymes also need to bind with some cofactors to fulfil their function. The active si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intron
An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e. a region inside a gene."The notion of the cistron .e., gene... must be replaced by that of a transcription unit containing regions which will be lost from the mature messenger – which I suggest we call introns (for intragenic regions) – alternating with regions which will be expressed – exons." (Gilbert 1978) The term ''intron'' refers to both the DNA sequence within a gene and the corresponding RNA sequence in RNA transcripts. The non-intron sequences that become joined by this RNA processing to form the mature RNA are called exons. Introns are found in the genes of most organisms and many viruses and they can be located in both protein-coding genes and genes that function as RNA (noncoding genes). There are four main types of introns: tRNA introns, group I introns, group II introns, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Model Organism
A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Model organisms are widely used to research human disease when human experimentation would be unfeasible or unethical. This strategy is made possible by the common descent of all living organisms, and the conservation of metabolic and developmental pathways and genetic material over the course of evolution. Studying model organisms can be informative, but care must be taken when generalizing from one organism to another. In researching human disease, model organisms allow for better understanding the disease process without the added risk of harming an actual human. The species chosen will usually meet a determined taxonomic equivalency to humans, so as to react to disease or its treatment in a way that resembles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saccharomyces Cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been originally isolated from the skin of grapes. It is one of the most intensively studied eukaryotic model organisms in molecular biology, molecular and cell biology, much like ''Escherichia coli'' as the model bacteria, bacterium. It is the microorganism behind the most common type of fermentation (biochemistry), fermentation. ''S. cerevisiae'' cells are round to ovoid, 5–10 micrometre, μm in diameter. It reproduces by budding. Many proteins important in human biology were first discovered by studying their Homology (biology), homologs in yeast; these proteins include cell cycle proteins, signaling proteins, and protein-processing enzymes. ''S. cerevisiae'' is currently the only yeast cell known to have Berkeley body, Berkeley bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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