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DCL3
DCL3 (an abbreviation of Dicer-like 3) is a gene in plants that codes for the DCL3 protein, a ribonuclease III enzyme involved in plants specific pathway RNA-directed DNA methylation. Where DCL3 cleaves endogenous double-stranded RNAs into 24 nucleotide small interfering RNAs. The main difference to other DCLs is the dsRNA source, which precursor for DCL3 is generally transcribed in heterochromatic regions by the RNA polymerase complex, RNA polymerase IV, producing single-stranded RNA roughly of 30 to 45 nucleotides in length, which are converted into dsRNA by RNA-dependent RNA polymerase 2. Once cleaved by DCL3, the 24-nt siRNA strand is loaded into AGO4, which interacts with Pol V–transcribed long noncoding RNAs and recruits domains-rearranged methylase 2, facilitating DNA methylation DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA-directed DNA Methylation
RNA-directed DNA methylation (RdDM) is a biological process in which non-coding RNA molecules direct the addition of DNA methylation to specific DNA sequences. The RdDM pathway is unique to plants, although other mechanisms of RNA-directed chromatin modification have also been described in fungi and animals. To date, the RdDM pathway is best characterized within angiosperms (flowering plants), and particularly within the model plant ''Arabidopsis thaliana''. However, conserved RdDM pathway components and associated small RNAs (sRNAs) have also been found in other groups of plants, such as gymnosperms and ferns. The RdDM pathway closely resembles other sRNA pathways, particularly the highly conserved RNAi pathway found in fungi, plants, and animals. Both the RdDM and RNAi pathways produce sRNAs and involve conserved Argonaute, Dicer and RNA-dependent RNA polymerase proteins. RdDM has been implicated in a number of regulatory processes in plants. The DNA methylation added by RdDM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DCL1
DCL1 (an abbreviation of Dicer-like 1) is a gene in plants that codes for the DCL1 protein, a ribonuclease III enzyme involved in processing double-stranded RNA (dsRNA) and microRNA (miRNA). Although DCL1, also called Endoribonuclease Dicer homolog 1, is named for its homology with the metazoan protein Dicer, its role in miRNA biogenesis is somewhat different, due to substantial differences in miRNA maturation processes between plants and animals, as well due to additional downstream plant-specific pathways, where DCL1 paralogs like DCL4 participate, such Trans-acting siRNA biogenesis. Function DCL1 is localized exclusively in the plant cell nucleus, together with the double-stranded RNA binding protein Hyponastic Leaves1 ( HYL1), CTD-Phosphatase-Like1 (CPL1) and the zinc finger protein SERRATE (SE), form nuclear dicing bodies or D-bodies. In these membraneless organelles, pri-miRNAs are recognized and processes into pre-miRNAs and subsecuently into mature miRNA duplexes, by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a basic unit of heredity and the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and noncoding genes. During gene expression, the DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Methylation
DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter, DNA methylation typically acts to repress gene transcription. In mammals, DNA methylation is essential for normal development and is associated with a number of key processes including genomic imprinting, X-chromosome inactivation, repression of transposable elements, aging, and carcinogenesis. As of 2016, two nucleobases have been found on which natural, enzymatic DNA methylation takes place: adenine and cytosine. The modified bases are N6-methyladenineD. B. Dunn, J. D. Smith: ''The occurrence of 6-methylaminopurine in deoxyribonucleic acids.'' In: ''Biochem J.'' 68(4), Apr 1958, S. 627–636. PMID 13522672. ., 5-methylcytosineB. F. Vanyushin, S. G. Tkacheva, A. N. Belozersky: ''Rare bases in animal DNA.'' In: ''Nature.'' 225, 1970, S. 948–949. PMID 4391887. and N4- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Long Non-coding RNA
Long non-coding RNAs (long ncRNAs, lncRNA) are a type of RNA, generally defined as transcripts more than 200 nucleotides that are not translated into protein. This arbitrary limit distinguishes long ncRNAs from small non-coding RNAs, such as microRNAs (miRNAs), small interfering RNAs (siRNAs), Piwi-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs), and other short RNAs. Long intervening/intergenic noncoding RNAs (lincRNAs) are sequences of lncRNA which do not overlap protein-coding genes. Long non-coding RNAs include intergenic lincRNAs, intronic ncRNAs, and sense and antisense lncRNAs, each type showing different genomic positions in relation to genes and exons. Abundance In 2007 a study found only one-fifth of transcription across the human genome is associated with protein-coding genes, indicating at least four times more long non-coding than coding RNA sequences. Large-scale complementary DNA (cDNA) sequencing projects such as FANTOM reveal the complexity of this t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pol V
DNA Polymerase V (Pol V) is a polymerase enzyme involved in DNA repair mechanisms in bacteria, such as ''Escherichia coli''. It is composed of a UmuD' homodimer and a UmuC monomer, forming the UmuD'2C protein complex. It is part of the Y-family of DNA Polymerases, which are capable of performing DNA translesion synthesis (TLS). Translesion polymerases bypass DNA damage lesions during DNA replication - if a lesion is not repaired or bypassed the replication fork can stall and lead to cell death. However, Y polymerases have low sequence fidelity during replication (prone to add wrong nucleotides). When the UmuC and UmuD' proteins were initially discovered in ''E. coli'', they were thought to be agents that inhibit faithful DNA replication and caused DNA synthesis to have high mutation rates after exposure to UV-light. The polymerase function of Pol V was not discovered until the late 1990s when UmuC was successfully extracted, consequent experiments unequivocally proved UmuD'2C is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AGO4
The Argonaute protein family, first discovered for its evolutionarily conserved stem cell function, plays a central role in RNA silencing processes as essential components of the RNA-induced silencing complex (RISC). RISC is responsible for the gene silencing phenomenon known as RNA interference (RNAi). Argonaute proteins bind different classes of small non-coding RNAs, including microRNAs (miRNAs), small interfering RNAs (siRNAs) and Piwi-interacting RNAs (piRNAs). Small RNAs guide Argonaute proteins to their specific targets through sequence complementarity (base pairing), which then leads to mRNA cleavage, translation inhibition, and/or the initiation of mRNA decay. The name of this protein family is derived from a mutant phenotype resulting from mutation of AGO1 in ''Arabidopsis thaliana'', which was likened by Bohmert et al. to the appearance of the pelagic octopus '' Argonauta argo''. RNA interference RNA interference (RNAi) is a biological process in which the RNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Polymerase IV
RNA polymerase IV (RNAP IV) is an enzyme that synthesizes small interfering RNA (siRNA) in plants, which silence gene expression. RNAP IV belongs to a family of enzymes that catalyze the process of transcription known as RNA Polymerases, which synthesize RNA from DNA templates. Discovered via phylogenetic studies of land plants, genes of RNAP IV are thought to have resulted from multistep evolution processes that occurred in RNA Polymerase II phylogenies. Such an evolutionary pathway is supported by the fact that RNAP IV is composed of 12 protein subunits that are either similar or identical to RNA polymerase II, and is specific to plant genomes. Via its synthesis of siRNA, RNAP IV is involved in regulation of heterochromatin formation in a process known as RNA directed DNA Methylation (RdDM). Discovery Phylogenetic Studies Phylogenetic studies of land plants have led to the discovery of RNA Polymerase IV. Analysis of the largestRPD1 and second-largest subunitsRPD2 of RNAP I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-stranded RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydrates, nucleic acids constitute one of the four major macromolecules essential for all known forms of life. Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA, RNA is 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. Some RNA molecules play an active role within cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
